Solve 2025 day 7

.gitignore

@@ -4,6 +4,8 @@
 __pycache__/
 *.py[cod]
 *$py.class
+.python-version
+uv.lock
 
 # C extensions
 *.so

2015/d1.py

@@ -1,8 +1,9 @@
-from lib import *
+from lib import get_data
 
-data = open(0).read()
+data = get_data(__file__)
 
-part_2 = True
+t = sum((1 if c == "(" else -1 for c in data))
+print(t)
 
 floor = 0
 for i, c in enumerate(data):
@@ -10,13 +11,6 @@ for i, c in enumerate(data):
         floor += 1
     elif c == ")":
         floor -= 1
-    else:
-        print(c)
-        assert False
-
-    if part_2 and floor == -1:
+    if floor == -1:
         print(i + 1)
         break
-
-if not part_2:
-    print(floor)

2015/d10.py

@@ -1,35 +1,29 @@
-from functools import lru_cache
-data = open(0).read().strip()
+from lib import get_data
 
-part_1 = False
-if part_1:
-    repeats = 40
-else:
-    repeats = 50
+data = get_data(__file__)
 
-@lru_cache
-def look_and_say(data: str) -> str:
-    r = ""
-    i = 0
-    while i < len(data):
-        count = 0
-        c = data[i]
-        while i < len(data) and data[i] == c:
+
+def iter(xs):
+    if not xs:
+        return []
+    grouped = []
+    current_element = xs[0]
+    count = 1
+    for element in xs[1:]:
+        if element == current_element:
             count += 1
-            i += 1
-        r += f"{count}{c}"
-    return r
+        else:
+            grouped.append(count)
+            grouped.append(current_element)
+            current_element = element
+            count = 1
+    grouped.append(count)
+    grouped.append(current_element)
+    return grouped
 
-CHUNK_SIZE = 10000
-for _ in range(repeats):
-    ndata = ""
-    lo, up = 0, CHUNK_SIZE
-    while up < len(data):
-        while up < len(data) and data[up - 1] == data[up]:
-            up += 1
-        ndata += look_and_say(data[lo:up])
-        lo, up = up, up + CHUNK_SIZE
-    ndata += look_and_say(data[lo:up])
-    data = ndata
 
-print(len(data))
+for repeat in [40, 50]:
+    xs = list(map(int, list(data.strip())))
+    for _ in range(repeat):
+        xs = iter(xs)
+    print(len(xs))

2015/d11.py

@@ -1,4 +1,7 @@
-data = open(0).read().strip()
+from lib import get_data
+
+data = get_data(__file__).strip()
+
 
 def is_valid(pw):
     # Passwords must include one increasing straight of at least three letters,
@@ -26,24 +29,26 @@ def is_valid(pw):
         return False
     return True
 
+
 def inc(pw):
     pw = list(map(ord, pw))
     for i in range(len(pw) - 1, -1, -1):
         pw[i] += 1
-        if pw[i] == ord('z') + 1:
-            pw[i] = ord('a')
+        if pw[i] == ord("z") + 1:
+            pw[i] = ord("a")
         else:
             break
     return "".join(map(chr, pw))
 
-part_1 = False
+
+part_1 = True
 valid_count = 0
 while True:
     data = inc(data)
     if is_valid(data):
         valid_count += 1
         if part_1 and valid_count == 1:
-        break
+            print(data)
         elif valid_count == 2:
+            print(data)
             break
-print(data)

2015/d12.py

@@ -1,27 +1,37 @@
+from lib import get_data
 import json
 
-data = open(0).read().strip()
-part_2 = False
+data = get_data(__file__).strip()
 
-def addup(d):
-    r = 0
-    if isinstance(d, list):
-        for e in d:
-            v = addup(e)
-            if v is not None:
-                r += v
-    elif isinstance(d, dict):
-        for e in d.values():
-            v = addup(e)
-            if v is None:
-                return 0
-            r += v
-    elif isinstance(d, str):
-        if part_2 and d == "red":
-            return None
+o = json.loads(data)
+
+
+def xsum(obj, part_2=False):
+    t = 0
+    if type(obj) is int:
+        t += obj
+    elif type(obj) is list:
+        for o in obj:
+            t += xsum(o, part_2)
+    elif type(obj) is dict:
+        if part_2:
+            st = 0
+            for o in obj.values():
+                st += xsum(o, part_2)
+                if type(o) is str and o == "red":
+                    break
             else:
-        r += d
-    return r
+                t += st
+        else:
+            for o in obj.values():
+                t += xsum(o, part_2)
+    elif type(obj) is str:
+        pass
+    else:
+        print(obj)
+        assert False
+    return t
 
-data = json.loads(data)
-print(addup(data))
+
+print(xsum(o))
+print(xsum(o, True))

2015/d13.py

@@ -1,35 +1,32 @@
+from lib import get_data
+from collections import defaultdict
 from itertools import permutations
-data = open(0).read().strip()
 
-part_2 = False
+data = get_data(__file__).strip()
 
+pairs = defaultdict(int)
 people = set()
-scores = {}
+
 for line in data.splitlines():
-    a, _, wl, score, _, _, _, _, _, _, b = line.split()
-    b = b.replace(".", "")
-    score = int(score)
-    if wl == "lose":
-        score = -score
+    a, _, gainlose, amount, _, _, _, _, _, _, b = line[:-1].split()
+    amount = int(amount)
+    if gainlose == "lose":
+        amount = -amount
+    pairs[(a, b)] = amount
     people.add(a)
-    people.add(b)
-    scores[(a, b)] = score
-    if part_2:
-        scores[(a, "me")] = 0
-        scores[("me", a)] = 0
-        scores[(b, "me")] = 0
-        scores[("me", b)] = 0
 
-if part_2:
-    people.add("me")
 
-max_score = 0
-for p in permutations(list(people)):
-    s = 0
-    for i in range(len(p)):
-        a, b = p[i], p[(i + 1) % len(p)]
-        s += scores[(a, b)]
-        s += scores[(b, a)]
-    max_score = max(max_score, s)
+def calc_gain(people):
+    maxgain = 0
+    for xs in permutations(list(people)):
+        gain = 0
+        for i in range(len(xs)):
+            gain += pairs[(xs[i], xs[(i + 1) % len(xs)])]
+            gain += pairs[(xs[(i + 1) % len(xs)], xs[i])]
+        maxgain = max(maxgain, gain)
+    return maxgain
 
-print(max_score)
+
+print(calc_gain(people))
+people.add("Felix")
+print(calc_gain(people))

2015/d14.py

@@ -1,53 +1,40 @@
-import lib
-data = open(0).read().strip()
+from lib import get_data
+from lib import ints, fst
+from collections import defaultdict
 
-part_1 = False
-
-rds = []
-max_dist = 0
-gtime = 2503
-rds = []
+data = get_data(__file__).strip()
+deers = []
 for line in data.splitlines():
-    speed, time, rest = lib.str_to_ints(line)
-    rds.append([speed, time, rest, 0, 0, 0])
-    speed *= 1000
+    speed, time, rest = ints(line)
+    deers.append([0, speed, time, rest, time, 0])
 
-    dist = 0
-    ctime = 0
-    while ctime < gtime:
-        t = min(time, gtime - ctime)
-        dist += (speed * t)
-        ctime += time
-        ctime += rest
-    max_dist = max(dist, max_dist)
+points = defaultdict(int)
+for _ in range(2503):
+    max_dists = defaultdict(list)
+    for i, deer in enumerate(deers):
+        dist, speed, time, rest, time_left, rest_left = deer
+        if time_left > 0:
+            time_left -= 1
+            dist += speed
+        elif time_left == 0:
+            time_left = -1
+            rest_left = rest - 1
+        elif rest_left > 0:
+            rest_left -= 1
+        elif rest_left == 0:
+            time_left = time - 1
+            dist += speed
+            rest_left = -1
+        max_dists[dist].append(i)
 
-if part_1:
-    print(max_dist // 1000)
+        deer[0] = dist
+        deer[4] = time_left
+        deer[5] = rest_left
 
-scores = [0 for _ in range(len(rds))]
-for _ in range(gtime):
-    for i in range(len(rds)):
-        speed, time, rest, dist, travel_time, rest_time = rds[i]
-        rd = rds[i]
-        if travel_time < time:
-            rd[3] += speed
-            rd[4] += 1
-        elif rest_time < rest:
-            rd[5] += 1
-            if rd[5] == rest:
-                rd[4] = 0
-                rd[5] = 0
+    max_deers = max(max_dists.items())
+    for di in max_deers[1]:
+        points[di] += 1
 
-    max_i = -1
-    max_v = 0
-    for i, rd in enumerate(rds):
-        if rd[3] > max_v:
-            max_i = i
-            max_v = rd[3]
-    for i, rd in enumerate(rds):
-        if rd[3] == max_v:
-            scores[i] += 1
-
-if not part_1:
-    print(max(scores))
 
+print(max(map(fst, deers)))
+print(max(points.values()))

2015/d2.py

@@ -1,19 +1,17 @@
-from lib import *
+from lib import get_data, ints
 
-data = open(0).readlines()
+data = get_data(__file__)
 
-part_1 = True
-if part_1:
-    a = 0
-    for line in data:
-        l, w, h = list(map(int, line.split("x")))
+a = 0
+for line in data.splitlines():
+    l, w, h = ints(line)
     slack = min([l * w, w * h, h * l])
-        a +=  (2*l*w + 2*w*h + 2*h*l + slack)
-else: 
-    a = 0
-    for line in data:
-        l, w, h = list(map(int, line.split("x")))
+    a += 2 * l * w + 2 * w * h + 2 * h * l + slack
+print(a)
+
+a = 0
+for line in data.splitlines():
+    l, w, h = ints(line)
     sd = min([2 * (l + w), 2 * (w + h), 2 * (h + l)])
     a += sd + (l * w * h)
-
 print(a)

2015/d20.py

@@ -4,6 +4,7 @@ import lib
 data = int(open(0).read().strip())
 part_1 = False
 
+
 def calc(n):
     fs = lib.prime_factors(n)
     vs = set([1, n])
@@ -21,6 +22,7 @@ def calc(n):
             r += e * 11
     return r
 
+
 for i in range(3, 10000000):
     c = calc(i)
     if c >= data:

2015/d3.py

@@ -1,9 +1,7 @@
-import sys
-from lib import *
+from lib import get_data
+from lib import V
 
-data = open(0).read()
-
-part_1 = False
+data = get_data(__file__)
 
 DIRS = {
     "^": (-1, 0),
@@ -12,30 +10,27 @@ DIRS = {
     "<": (0, -1),
 }
 
-if part_1:
-    pos = (0, 0)
-    poss = set([pos])
+pos = V(0, 0)
+poss = set([pos])
 
-    for c in data:
+for c in data:
     d = DIRS[c]
-        pos = pos[0] + d[0], pos[1] + d[1]
+    pos = pos + d
     poss.add(pos)
 
-    print(len(poss))
-    sys.exit(0)
+print(len(poss))
 
-a = (0, 0)
-b = (0, 0)
+a = V(0, 0)
+b = V(0, 0)
 poss = set([a, b])
 for i, c in enumerate(data):
     if i % 2 == 0:
         d = DIRS[c]
-        a = a[0] + d[0], a[1] + d[1]
+        a = a + d
         poss.add(a)
     else:
         d = DIRS[c]
-        b = b[0] + d[0], b[1] + d[1]
+        b = b + d
         poss.add(b)
 
 print(len(poss))
-sys.exit(0)

2015/d4.py

@@ -1,16 +1,10 @@
-from lib import *
+from lib import get_data
 import hashlib
 
-part_1 = True
+data = get_data(__file__).strip()
 
-if part_1:
-    digits = 5
-else:
-    digits = 6
-
-data = open(0).read().strip()
-
-for i in range(10**9):
+for digits in [5, 6]:
+    for i in range(10**9):
         text = data + str(i)
         md5_hash = hashlib.md5(text.encode()).hexdigest()
         for c in md5_hash[:digits]:
@@ -19,4 +13,3 @@ for i in range(10**9):
         else:
             print(i)
             break
-

2015/d5.py

@@ -1,53 +1,56 @@
-from lib import *
+from lib import get_data
 
-data = open(0).read()
+data = get_data(__file__)
 
-part_1 = True
-if part_1:
-    res = 0
-    for line in data.splitlines():
+
+def is_nice(line):
+    # It contains at least three vowels (aeiou only), like aei, xazegov, or aeiouaeiouaeiou.
     vc = 0
-        for c in line:
-            if c in "aoeui":
-                vc += 1
+    for v in "aeiou":
+        vc += line.count(v)
     if vc < 3:
-            continue
+        return False
 
-        prev = None
-        for c in line:
-            if c == prev:
-                break
-            prev = c
-        else:
-            continue
-
-        contains = False
-        ss = ["ab", "cd", "pq", "xy"]
-        for s in ss:
-            if s in line:
-                contains = True
-
-        if contains:
-            continue
-        res += 1
-    print(res)
-else:
-    res = 0
-    for line in data.splitlines():
-        pairs = {}
-        for i in range(0, len(line) - 1):
-            p = line[i:i+2]
-            if p in pairs and i > pairs[p] + 1:
-                break
-            if not p in pairs:
-                pairs[p] = i
-        else:
-            continue
-
-        for i in range(0, len(line) - 2):
-            if line[i] == line[i + 2]:
+    # It contains at least one letter that appears twice in a row, like xx,
+    # abcdde (dd), or aabbccdd (aa, bb, cc, or dd).
+    for i in range(len(line) - 1):
+        if line[i] == line[i + 1]:
             break
     else:
-            continue
-        res += 1
-    print(res)
+        return False
+
+    # It does not contain the strings ab, cd, pq, or xy, even if they are
+    # part of one of the other requirements.
+    for i in range(len(line) - 1):
+        cc = "".join(line[i : i + 2])
+        if cc in ["ab", "cd", "pq", "xy"]:
+            return False
+    return True
+
+
+def is_nice_2(line):
+    good = False
+    for i in range(len(line) - 1):
+        cc = "".join(line[i : i + 2])
+        for j in range(i + 2, len(line) - 1):
+            dd = "".join(line[j : j + 2])
+            if cc == dd:
+                good = True
+    if not good:
+        return False
+
+    for i in range(len(line) - 2):
+        cc = "".join(line[i : i + 3])
+        if cc[0] == cc[2]:
+            break
+    else:
+        return False
+    return True
+
+
+t = sum(1 if is_nice(line) else 0 for line in data.splitlines())
+print(t)
+
+
+t = sum(1 if is_nice_2(line) else 0 for line in data.splitlines())
+print(t)

2015/d6.py

@@ -1,33 +1,29 @@
-from lib import *
+from lib import get_data, ints
+from collections import defaultdict as DD
 
-data = open(0).read()
-
-part_2 = True
-lights = [[0 for _ in range(1000)] for _ in range(1000)]
+data = get_data(__file__)
 
+ons = set()
+ons2 = DD(int)
 for line in data.splitlines():
-    x1, y1, x2, y2 = str_to_ints(line)
+    x1, y1, x2, y2 = ints(line)
     for x in range(x1, x2 + 1):
         for y in range(y1, y2 + 1):
-            if part_2:
-                if "on" in line:
-                    lights[x][y] += 1
-                elif "off" in line:
-                    lights[x][y] = max(0, lights[x][y] - 1)
+            if "off" in line:
+                if (x, y) in ons:
+                    ons.remove((x, y))
+                ons2[(x, y)] = max(ons2[(x, y)] - 1, 0)
+            elif "on" in line:
+                ons.add((x, y))
+                ons2[(x, y)] += 1
+            elif "toggle" in line:
+                if (x, y) in ons:
+                    ons.remove((x, y))
                 else:
-                    lights[x][y] += 2
+                    ons.add((x, y))
+                ons2[(x, y)] += 2
             else:
-                if "on" in line:
-                    lights[x][y] = 1
-                elif "off" in line:
-                    lights[x][y] = 0
-                else:
-                    if lights[x][y] == 1:
-                        lights[x][y] = 0
-                    else:
-                        lights[x][y] = 1
+                assert False
 
-res = 0
-for row in lights:
-    res += sum(row)
-print(res)
+print(len(ons))
+print(sum(ons2.values()))

2015/d7.py

@@ -1,90 +1,54 @@
-from lib import *
+from lib import get_data
 
-data = open(0).read()
+data = get_data(__file__)
 
-part_2 = False
-if part_2:
-    gates = {"b": 16076}
-else:
-    gates = {}
 
-while "a" not in gates:
+def run(wires={}):
+    def get(a):
+        try:
+            return int(a)
+        except ValueError:
+            pass
+        if a in wires:
+            return wires[a]
+        else:
+            return None
+
+    while "a" not in wires:
         for line in data.splitlines():
             lhs, rhs = line.split(" -> ")
-        if part_2 and rhs == "b":
+            if rhs in wires:
                 continue
-        lhs = lhs.strip()
-        if "NOT" in lhs:
-            op, op1 = lhs.split(" ")
-            assert op == "NOT"
-            try:
-                op1 = int(op1)
-                gates[rhs] = ~op1 & 0xffff
-            except ValueError:
-                if op1 in gates and isinstance(gates[op1], int):
-                    gates[rhs] = ~gates[op1] & 0xffff
-        elif "OR" in lhs:
-            op1, op, op2 = lhs.split(" ")
-            assert op == "OR"
-            try:
-                op1 = int(op1)
-            except ValueError:
-                if op1 in gates and isinstance(gates[op1], int):
-                    op1 = gates[op1]
-            try:
-                op2 = int(op2)
-            except ValueError:
-                if op2 in gates and isinstance(gates[op2], int):
-                    op2 = gates[op2]
+            match lhs.split():
+                case [a, "AND", b]:
+                    a, b = get(a), get(b)
+                    if a is not None and b is not None:
+                        wires[rhs] = a & b
+                case [a, "OR", b]:
+                    a, b = get(a), get(b)
+                    if a is not None and b is not None:
+                        wires[rhs] = a | b
+                case [a, "LSHIFT", b]:
+                    a, b = get(a), get(b)
+                    if a is not None and b is not None:
+                        wires[rhs] = a << b
+                case [a, "RSHIFT", b]:
+                    a, b = get(a), get(b)
+                    if a is not None and b is not None:
+                        wires[rhs] = a >> b
+                case ["NOT", a]:
+                    a = get(a)
+                    if a is not None:
+                        wires[rhs] = ~a & 0xFFFF
+                case [a]:
+                    a = get(a)
+                    if a is not None:
+                        wires[rhs] = a
+    return wires
 
-            if not (isinstance(op1, int) and isinstance(op2, int)):
-                continue
-            gates[rhs] = (op1 | op2) 
-        elif "AND" in lhs:
-            op1, op, op2 = lhs.split(" ")
-            assert op == "AND"
-            try:
-                op1 = int(op1)
-            except ValueError:
-                if op1 in gates and isinstance(gates[op1], int):
-                    op1 = gates[op1]
-            try:
-                op2 = int(op2)
-            except ValueError:
-                if op2 in gates and isinstance(gates[op2], int):
-                    op2 = gates[op2]
 
-            if not (isinstance(op1, int) and isinstance(op2, int)):
-                continue
-            gates[rhs] = (op1 & op2) 
-        elif "LSHIFT" in lhs:
-            op1, op, op2 = lhs.split(" ")
-            op2 = int(op2)
-            try:
-                op1 = int(op1)
-            except ValueError:
-                if op1 in gates:
-                    op1 = gates[op1]
-                else:
-                    continue
-            gates[rhs] = (op1 << op2) & 0xffff
-        elif "RSHIFT" in lhs:
-            op1, op, op2 = lhs.split(" ")
-            op2 = int(op2)
-            try:
-                op1 = int(op1)
-            except ValueError:
-                if op1 in gates:
-                    op1 = gates[op1]
-                else:
-                    continue
-            gates[rhs] = (op1 >> op2) & 0xffff
-        else:
-            try:
-                lhs = int(lhs)
-                gates[rhs] = lhs
-            except ValueError:
-                if lhs in gates:
-                    gates[rhs] = gates[lhs]
+a = run()["a"]
+print(a)
 
-print(gates["a"])
+a2 = run(wires={"b": a})["a"]
+print(a2)

2015/d8.py

@@ -1,26 +1,25 @@
-from lib import *
+from lib import get_data
+import re
 
-data = open(0).read()
-part_1 = False
+data = get_data(__file__)
 
-if part_1:
-    r1 = re.compile(r"\\x[0-9a-f][0-9a-f]")
-    r2 = re.compile(r"\\\\")
-    r3 = re.compile(r"\\\"")
+r1 = re.compile(r"\\x[0-9a-f][0-9a-f]")
+r2 = re.compile(r"\\\\")
+r3 = re.compile(r"\\\"")
 
-    enc, mem = 0, 0
-    for line in data.splitlines():
+enc, mem = 0, 0
+for line in data.splitlines():
     mem += len(line)
     line = r1.sub("^", line)
     line = r2.sub("^", line)
     line = r3.sub("^", line)
     enc += len(line) - 2
-    print(mem - enc)
-else:
-    ori, enc = 0, 0
-    for line in data.splitlines():
+print(mem - enc)
+
+ori, enc = 0, 0
+for line in data.splitlines():
     ori += len(line)
     line = line.replace("\\", "\\\\")
-        line = line.replace("\"", "\\\"")
+    line = line.replace('"', '\\"')
     enc += len(line) + 2
-    print(enc - ori)
+print(enc - ori)

2015/d9.py

@@ -1,42 +1,27 @@
-from lib import *
-from typing import Iterator
+from lib import get_data
+from itertools import permutations
 
-# Just for fun instead of using itertools.permutations.
-def permutations(xs) -> Iterator:
-    assert len(xs) > 0
-    if len(xs) == 1:
-        yield xs
-    else:
-        x = xs.pop()
-        for p in permutations(xs):
-            for i in range(len(p) + 1):
-                pn = list(p)
-                pn.insert(i, x)
-                yield pn
-
-part_1 = False
-data = open(0).read()
+data = get_data(__file__)
 
 dists = {}
 nodes = set()
 for line in data.splitlines():
-    path, dist = line.split(" = ")
-    dist = int(dist)
-    a, b = path.split(" to ")
+    a, _, b, _, d = line.split()
     nodes.add(a)
     nodes.add(b)
+    dist = int(d)
     dists[(a, b)] = dist
     dists[(b, a)] = dist
 
-if part_1:
-    mdist = 10**12
-    for route in permutations(nodes):
-        dist = sum([dists[(route[i], route[i + 1])] for i in range(len(route) - 1)])
-        mdist = min(dist, mdist)
-    print(mdist)
-else:
-    mdist = 0
-    for route in permutations(nodes):
-        dist = sum([dists[(route[i], route[i + 1])] for i in range(len(route) - 1)])
-        mdist = max(dist, mdist)
-    print(mdist)
+d_min = 10**12
+d_max = 0
+for p in permutations(list(nodes)):
+    d = 0
+    for i in range(len(p) - 1):
+        a, b = p[i], p[i + 1]
+        d += dists[(a, b)]
+    d_min = min(d, d_min)
+    d_max = max(d, d_max)
+
+print(d_min)
+print(d_max)

2018/d10.py

@@ -0,0 +1,54 @@
+from lib import str_to_ints
+
+
+def print_points(objs):
+    x_min, x_max = 10**9, 0
+    y_min, y_max = 10**9, 0
+
+    exist = set()
+    for x, y, _, _ in objs:
+        x_min = min(x_min, x)
+        y_min = min(y_min, y)
+        x_max = max(x_max, x)
+        y_max = max(y_max, y)
+        exist.add((x, y))
+
+    if x_max - x_min > 67:
+        return False
+
+    for y in range(y_min, y_max + 1):
+        s = ""
+        for x in range(x_min, x_max + 1):
+            if (x, y) in exist:
+                s += "X"
+            else:
+                s += " "
+        print(s)
+    return True
+
+
+def part_1(data):
+    objs = []
+    for line in data.splitlines():
+        x, y, dx, dy = str_to_ints(line)
+        objs.append((x,y, dx, dy))
+
+    for t in range(1_000_000):
+        for i in range(len(objs)):
+            x, y, dx, dy = objs[i]
+            on = (x + dx, y + dy, dx, dy)
+            objs[i] = on
+        if print_points(objs):
+            print(t + 1)
+            break
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d11.py

@@ -0,0 +1,80 @@
+from functools import lru_cache
+
+
+@lru_cache
+def score(serial, x, y):
+    # Find the fuel cell's rack ID, which is its X coordinate plus 10.
+    # Begin with a power level of the rack ID times the Y coordinate.
+    # Increase the power level by the value of the grid serial number (your puzzle input).
+    # Set the power level to itself multiplied by the rack ID.
+    # Keep only the hundreds digit of the power level (so 12345 becomes 3; numbers with no hundreds digit become 0).
+    # Subtract 5 from the power level.
+    rack_id = x + 10
+    power_level = rack_id * y
+    power_level += serial
+    power_level *= rack_id
+    try:
+        return int(str(power_level)[-3]) - 5
+    except IndexError:
+        return -5
+
+
+def part_1(data):
+    v = int(data.strip())
+    max_val = 0
+    max_coord = None
+
+    assert score(8, 3, 5) == 4
+    assert score(57, 122, 79) == -5
+    assert score(39, 217, 196) == 0
+
+    for x in range(1, 299):
+        for y in range(1, 299):
+            s = 0
+            for x2 in range(x, x + 3):
+                for y2 in range(y, y + 3):
+                    s += score(v, x2, y2)
+                    if x2 > 300 or y2 > 300:
+                        assert False
+            if s > max_val:
+                max_val = s
+                max_coord = (x, y)
+    assert max_coord is not None
+    print(",".join(list(map(str, max_coord))))
+
+
+def part_2(data):
+    v = int(data.strip())
+    max_val = 0
+    max_coord = None
+
+    # brute force, just tried if 15 is small enough
+    for size in range(2, 15):
+        for x in range(1, 299):
+            for y in range(1, 299):
+                s = 0
+                if x + size > 300 or y + size > 300:
+                    break
+
+                for x2 in range(x, x + size):
+                    for y2 in range(y, y + size):
+                        s += score(v, x2, y2)
+                        if x2 > 300 or y2 > 300:
+                            assert False
+                if s > max_val:
+                    max_val = s
+                    max_coord = (x, y, size)
+    assert max_coord is not None
+    print(",".join(list(map(str, max_coord))))
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d12.py

@@ -0,0 +1,60 @@
+def score(state, offset):
+    r = 0
+    for i in range(len(state)):
+        if state[i] == "#":
+            r += i + offset
+    return r
+
+
+def solve(data, target_i):
+    state = None
+    map = {}
+    for line in data.splitlines():
+        if "initial state" in line:
+            _, rest = line.split(":")
+            state = rest.strip()
+        if "=>" in line:
+            lhs, rhs = line.split(" => ")
+            assert lhs not in map
+            map[lhs] = rhs
+
+    assert state is not None
+    seen = {}
+    offset = 0
+    for i in range(target_i):
+        while not state.startswith("...."):
+            state = "." + state
+            offset -= 1
+        while not state.endswith("...."):
+            state += "."
+
+        if state in seen:
+            prev_i, prev_score = seen[state]
+            assert (i - prev_i) == 1
+            current_score = score(state, offset)
+            delta_score = current_score - prev_score
+            final_score = current_score + (target_i - i) * delta_score
+            print(final_score)
+            return
+        else:
+            seen[state] = (i, score(state, offset))
+
+        ns = ""
+        for i in range(2, len(state) - 2):
+            s = state[i - 2 : i + 3]
+            ns += map[s]
+        state = ns
+        offset += 2
+    print(score(state, offset))
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    solve(data, 20)
+    solve(data, 50 * 10**9)
+
+
+if __name__ == "__main__":
+    main()

2018/d13.py

@@ -0,0 +1,102 @@
+from lib import Grid2D, add2
+
+CARTS = (
+    ("^", Grid2D.N, "|"),
+    ("v", Grid2D.S, "|"),
+    (">", Grid2D.E, "-"),
+    ("<", Grid2D.W, "-"),
+)
+TURNS = "lsr"
+DIRS = [(-1, 0), (0, 1), (1, 0), (0, -1)]
+
+
+def part_1(data):
+    g = Grid2D(data)
+    first_shown = False
+    carts = []
+    occupied = set()
+
+    for c, d, r in CARTS:
+        for cart in g.find(c):
+            carts.append((cart, d, "l"))
+            g[cart] = r
+            occupied.add(cart)
+
+    for _ in range(1, 100_000):
+        carts = sorted(carts)
+
+        ncarts = []
+        i_to_skip = []
+        for i in range(len(carts)):
+            if i in i_to_skip:
+                continue
+
+            pos, dir, turn = carts[i]
+            occupied.remove(pos)
+            pos = add2(pos, dir)
+
+            # detect collision and remove carts
+            if pos in occupied:
+                if first_shown is False:
+                    print(f"{pos[1]},{pos[0]}")
+                    first_shown = True
+                # either from carts that haven't moved, yet
+                for j in range(len(carts)):
+                    jpos, _, _ = carts[j]
+                    if jpos == pos:
+                        i_to_skip.append(j)
+                        break
+                else:
+                    # or from carts that have already moved
+                    ncarts = list(filter(lambda c: c[0] != pos, ncarts))
+                occupied.remove(pos)
+                continue
+            else:
+                occupied.add(pos)
+
+            if g[pos] == "+":
+                if turn == "l":
+                    dir = DIRS[(DIRS.index(dir) - 1) % len(DIRS)]
+                elif turn == "r":
+                    dir = DIRS[(DIRS.index(dir) + 1) % len(DIRS)]
+                turn = TURNS[(TURNS.index(turn) + 1) % len(TURNS)]
+            elif g[pos] == "/":
+                if dir == g.E:
+                    dir = g.N
+                elif dir == g.W:
+                    dir = g.S
+                elif dir == g.N:
+                    dir = g.E
+                elif dir == g.S:
+                    dir = g.W
+                else:
+                    assert False
+            elif g[pos] == "\\":
+                if dir == g.E:
+                    dir = g.S
+                elif dir == g.W:
+                    dir = g.N
+                elif dir == g.N:
+                    dir = g.W
+                elif dir == g.S:
+                    dir = g.E
+                else:
+                    assert False
+
+            ncarts.append((pos, dir, turn))
+        carts = ncarts
+        if len(carts) == 1:
+            pos = carts[0][0]
+            print(f"{pos[1]},{pos[0]}")
+            return
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d14.py

@@ -0,0 +1,62 @@
+def part_1(data):
+    num = int(data.strip())
+    recipes = [3, 7]
+    i, j = 0, 1
+
+    while True:
+        s = recipes[i] + recipes[j]
+        ss = str(s)
+        if len(ss) == 1:
+            recipes.append(s)
+        elif len(ss) == 2:
+            recipes.append(int(ss[0]))
+            recipes.append(int(ss[1]))
+        else:
+            assert False
+
+        i = (i + 1 + recipes[i]) % len(recipes)
+        j = (j + 1 + recipes[j]) % len(recipes)
+        if i == j:
+            j = (j + 1) % len(recipes)
+        if len(recipes) > num + 10:
+            print("".join(map(str, recipes[num : num + 10])))
+            break
+
+
+def part_2(data):
+    target = list(map(int, data.strip()))
+    recipes = [3, 7]
+
+    i, j = 0, 1
+    while True:
+        s = recipes[i] + recipes[j]
+        if s < 10:
+            recipes.append(s)
+        elif s < 100:
+            recipes.append(s // 10)
+            recipes.append(s % 10)
+        else:
+            assert False
+
+        i = (i + 1 + recipes[i]) % len(recipes)
+        j = (j + 1 + recipes[j]) % len(recipes)
+        if i == j:
+            j = (j + 1) % len(recipes)
+
+        if recipes[-len(target) :] == target:
+            print(len(recipes) - len(target))
+        elif recipes[-len(target) - 1 : -1] == target:
+            print(len(recipes) - len(target) - 1)
+            break
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d15.py

@@ -0,0 +1,117 @@
+from lib import Grid2D, add2
+from collections import deque
+
+
+DIRS = [Grid2D.N, Grid2D.W, Grid2D.E, Grid2D.S]
+
+
+def find_move(unit, grid):
+    assert grid[unit] in "GE"
+    target_fields = set()
+    enemies = grid.find("G") if grid[unit] == "E" else grid.find("E")
+    for e in enemies:
+        for dir in DIRS:
+            nb = add2(e, dir)
+            if grid[nb] == ".":
+                target_fields.add(nb)
+
+    # we are already next to an enemy
+    if unit in target_fields:
+        return None
+
+    seen = set()
+    states = deque([(unit, [])])
+    while states:
+        pos, hist = states.popleft()
+
+        if pos in seen:
+            continue
+        else:
+            seen.add(pos)
+
+        for dir in DIRS:
+            nb = add2(pos, dir)
+            if nb in target_fields:
+                if hist:
+                    return hist[0]
+                else:
+                    return nb
+            elif grid[nb] == ".":
+                nhist = hist + [nb]
+                states.append((nb, nhist))
+
+    # we did not find a path to an enemy
+    return None
+
+
+def part_2(data):
+    for elf_attack in range(3, 100):
+        g = Grid2D(data)
+        pos_to_health = {pos: 200 for pos in g.find("GE")}
+        len_elfs_orig = len(g.find("E"))
+
+        rounds = 0
+        done = False
+        while not done:
+            for unit in sorted(list(pos_to_health.keys())):
+                if not unit in pos_to_health:
+                    continue  # unit died in the meantime
+                enemy_type = "G" if g[unit] == "E" else "E"
+
+                # move stage
+                for dir in DIRS:
+                    nb = add2(unit, dir)
+                    if g[nb] == enemy_type:
+                        break  # we are already next to an enemy
+                else:
+                    npos = find_move(unit, g)
+                    if npos is not None:
+                        assert npos not in pos_to_health and g[npos] == "."
+                        pos_to_health[npos] = pos_to_health[unit]
+                        del pos_to_health[unit]
+                        g[npos] = g[unit]
+                        g[unit] = "."
+                        unit = npos
+
+                # attack stage
+                enemy_type = "G" if g[unit] == "E" else "E"
+                enemy_hit = 999
+                enemy = None
+                for dir in DIRS:
+                    nb = add2(unit, dir)
+                    if g[nb] == enemy_type and pos_to_health[nb] < enemy_hit:
+                        enemy_hit = pos_to_health[nb]
+                        enemy = nb
+
+                if enemy is not None:
+                    if g[enemy] == "G":
+                        pos_to_health[enemy] -= elf_attack
+                    else:
+                        pos_to_health[enemy] -= 3
+                    if pos_to_health[enemy] <= 0:
+                        del pos_to_health[enemy]
+                        g[enemy] = "."
+
+                if len(g.find("E")) == 0 or len(g.find("G")) == 0:
+                    done = True
+                    break
+            else:
+                rounds += 1
+
+        if elf_attack == 3:
+            print(sum(pos_to_health.values()) * rounds)
+
+        if len(g.find("E")) == len_elfs_orig:
+            print(sum(pos_to_health.values()) * (rounds))
+            break
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d16.py

@@ -0,0 +1,147 @@
+from lib import str_to_ints, get_data
+
+
+def addr(regs, a, b, c):
+    regs[c] = regs[a] + regs[b]
+
+
+def addi(regs, a, b, c):
+    regs[c] = regs[a] + b
+
+
+def mulr(regs, a, b, c):
+    regs[c] = regs[a] * regs[b]
+
+
+def muli(regs, a, b, c):
+    regs[c] = regs[a] * b
+
+
+def banr(regs, a, b, c):
+    regs[c] = regs[a] & regs[b]
+
+
+def bani(regs, a, b, c):
+    regs[c] = regs[a] & b
+
+
+def borr(regs, a, b, c):
+    regs[c] = regs[a] | regs[b]
+
+
+def bori(regs, a, b, c):
+    regs[c] = regs[a] | b
+
+
+def setr(regs, a, _, c):
+    regs[c] = regs[a]
+
+
+def seti(regs, a, _, c):
+    regs[c] = a
+
+
+def gtir(regs, a, b, c):
+    regs[c] = 1 if a > regs[b] else 0
+
+
+def gtri(regs, a, b, c):
+    regs[c] = 1 if regs[a] > b else 0
+
+
+def gtrr(regs, a, b, c):
+    regs[c] = 1 if regs[a] > regs[b] else 0
+
+
+def eqir(regs, a, b, c):
+    regs[c] = 1 if a == regs[b] else 0
+
+
+def eqri(regs, a, b, c):
+    regs[c] = 1 if regs[a] == b else 0
+
+
+def eqrr(regs, a, b, c):
+    regs[c] = 1 if regs[a] == regs[b] else 0
+
+
+OPS = [
+    addr,
+    addi,
+    mulr,
+    muli,
+    banr,
+    bani,
+    borr,
+    bori,
+    setr,
+    seti,
+    gtir,
+    gtri,
+    gtrr,
+    eqir,
+    eqri,
+    eqrr,
+]
+
+
+def part_1(data):
+    examples = []
+
+    lines = data.splitlines()
+    test_prog = []
+    last_i = None
+    for i in range(len(lines)):
+        line = lines[i]
+        if line.startswith("Before:"):
+            regs = str_to_ints(line)
+            inst = str_to_ints(lines[i + 1])
+            regs_after = str_to_ints(lines[i + 2])
+            examples.append((regs, inst, regs_after))
+            last_i = i + 2
+
+    assert last_i is not None
+    for line in lines[last_i:]:
+        if line.strip() != "":
+            test_prog.append(str_to_ints(line))
+
+    r = 0
+    for before_orig, inst, after in examples:
+        ops_correct = []
+        for op in OPS:
+            before = list(before_orig)
+            op(before, *inst[1:])
+            if before == after:
+                ops_correct.append(op)
+        if len(ops_correct) >= 3:
+            r += 1
+    print(r)
+
+    code_to_op = {}
+    while len(OPS) > 0:
+        for before_orig, inst, after in examples:
+            ops_correct = []
+            for op in OPS:
+                before = list(before_orig)
+                op(before, *inst[1:])
+                if before == after:
+                    ops_correct.append(op)
+            if len(ops_correct) == 1:
+                code_to_op[inst[0]] = ops_correct[0]
+                OPS.remove(ops_correct[0])
+
+    regs = [0, 0, 0, 0]
+    for line in test_prog:
+        op_code = line[0]
+        vals = line[1:]
+        code_to_op[op_code](regs, *vals)
+    print(regs[0])
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d17.py

@@ -0,0 +1,136 @@
+from lib import get_data, str_to_ints, add2
+
+
+def above(p):
+    return add2(p, (0, -1))
+
+
+def below(p):
+    return add2(p, (0, 1))
+
+
+def right(p):
+    return add2(p, (1, 0))
+
+
+def left(p):
+    return add2(p, (-1, 0))
+
+
+def print2d(xs, ys=[], zs=[], cs=".#~|"):
+    xs, ys, zs = set(xs), set(ys), set(zs)
+    all = xs | ys | zs
+    x_min, x_max, y_min, y_max = 10**9, 0, 10**9, 0
+    for x, y in all:
+        x_min = min(x_min, x)
+        y_min = min(y_min, y)
+        x_max = max(x_max, x)
+        y_max = max(y_max, y)
+    for y in range(y_min, y_max + 1):
+        row = ""
+        for x in range(x_min, x_max + 1):
+            if (x, y) in xs:
+                row += cs[1]
+            elif (x, y) in ys:
+                row += cs[2]
+            elif (x, y) in zs:
+                row += cs[3]
+            else:
+                row += cs[0]
+        print(row)
+
+
+def part_1(data):
+    sand = []
+    max_y = 0
+    min_y = 10**9
+    for line in data.splitlines():
+        line = line.strip()
+        a, b, c = str_to_ints(line)
+        if line.startswith("x"):
+            x = a
+            for y in range(b, c + 1):
+                max_y = max(max_y, y)
+                min_y = min(min_y, y)
+                sand.append((x, y))
+        elif line.startswith("y"):
+            y = a
+            max_y = max(max_y, y)
+            min_y = min(min_y, y)
+            for x in range(b, c + 1):
+                sand.append((x, y))
+        else:
+            assert False
+
+    # TODO: probably should use 2D array for better perf
+    sources = [(500, 0)]
+    water = set()
+    sand = set(sand)
+    water_rest = set()
+
+    while sources:
+        source = sources.pop()
+        current = below(source)
+        while current[1] <= max_y:
+            if current[1] < min_y:
+                current = below(current)
+            elif current in water_rest:
+                break
+            elif below(current) in sand or below(current) in water_rest:
+                water.add(current)
+                c = current
+                to_water_rest = [current]
+                left_sand, right_sand = False, False
+                while True:
+                    c = right(c)
+                    if c in sand:
+                        right_sand = True
+                        break
+                    elif below(c) in sand or below(c) in water_rest:
+                        water.add(c)
+                        to_water_rest.append(c)
+                    else:
+                        # it's empty underneath
+                        water.add(c)
+                        sources.append(c)
+                        break
+
+                c = current
+                while True:
+                    c = left(c)
+                    if c in sand:
+                        left_sand = True
+                        break
+                    elif below(c) in sand or below(c) in water_rest:
+                        water.add(c)
+                        to_water_rest.append(c)
+                    else:
+                        # it's empty underneath
+                        water.add(c)
+                        sources.append(c)
+                        break
+
+                if left_sand and right_sand:
+                    sources.append(above(above(current)))
+                    for w in to_water_rest:
+                        water_rest.add(w)
+                break
+            else:
+                water.add(current)
+                current = below(current)
+
+        # print2d(sand, water_rest, water)
+        # print(sources)
+        # input()
+    current_water = len(water_rest | water)
+    print(current_water)
+    print(len(water_rest))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2018/d18.py

@@ -0,0 +1,68 @@
+from lib import get_data, Grid2D
+from copy import deepcopy
+
+
+def part_2(data, target=10):
+    g = Grid2D(data)
+    seen = {}
+    i = 0
+    while i < target:
+        ng = deepcopy(g)
+        for r in range(g.n_rows):
+            for c in range(g.n_cols):
+                if g[(r, c)] == ".":
+                    tree_count = sum(
+                        [1 if g[nb] == "|" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    if tree_count >= 3:
+                        ng[(r, c)] = "|"
+                elif g[(r, c)] == "|":
+                    lumber_count = sum(
+                        [1 if g[nb] == "#" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    if lumber_count >= 3:
+                        ng[(r, c)] = "#"
+                elif g[(r, c)] == "#":
+                    tree_count = sum(
+                        [1 if g[nb] == "|" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    lumber_count = sum(
+                        [1 if g[nb] == "#" else 0 for nb in g.neighbors_adj((r, c))]
+                    )
+                    if tree_count > 0 and lumber_count > 0:
+                        pass
+                    else:
+                        ng[(r, c)] = "."
+                else:
+                    assert False
+
+        h = ng.hash()
+        if h in seen:
+            delta = i - seen[h]
+            while (i + delta) < target:
+                i += delta
+            seen = {}
+        else:
+            seen[h] = i
+        i += 1
+        g = ng
+
+    w = 0
+    l = 0
+    for r in range(g.n_rows):
+        for c in range(g.n_cols):
+            if g[(r, c)] == "|":
+                w += 1
+            elif g[(r, c)] == "#":
+                l += 1
+    print(l * w)
+
+
+def main():
+    data = get_data(__file__)
+    part_2(data, 10)
+    part_2(data, 1000000000)
+
+
+if __name__ == "__main__":
+    main()

2018/d19.py

@@ -0,0 +1,134 @@
+from lib import get_data, str_to_ints
+import d16
+
+
+def print_regs(regs):
+    print(" ".join([f"regs[{i}]={regs[i]:10}" for i in range(len(regs))]) + " (ip)")
+
+
+def print_inst(i, insts, ip):
+    op, arg1, arg2, dest = insts[i]
+    dest = f"regs[{dest}]" if dest != ip else "ip"
+    match op:
+        case "addi":
+            print(f"{i:2} {dest} = regs[{arg1}] + {arg2}")
+        case "addr":
+            print(f"{i:2} {dest} = regs[{arg1}] + regs[{arg2}]")
+        case "muli":
+            print(f"{i:2} {dest} = regs[{arg1}] * {arg2}")
+        case "mulr":
+            print(f"{i:2} {dest} = regs[{arg1}] * regs[{arg2}]")
+        case "seti":
+            print(f"{i:2} {dest} = {arg1}")
+        case "setr":
+            print(f"{i:2} {dest} = regs[{arg1}]")
+        case "eqrr":
+            print(f"{i:2} {dest} = (regs[{arg1}] == regs[{arg2}]) ? 1 : 0")
+        case "gtrr":
+            print(f"{i:2} {dest} = (regs[{arg1}] > regs[{arg2}]) ? 1 : 0")
+        case _:
+            print(f"{i:2} {dest} = {op}({arg1}, {arg2})")
+
+
+def sum_of_divisors(n):
+    total = 1
+    for i in range(2, int(n**0.5) + 1):
+        if n % i == 0:
+            total += i
+            if i != n // i:  # do not count square root twice
+                total += n // i
+    if n != 1:
+        total += n
+    return total
+
+
+def run(data, break_after=None, reg_zero_init=0):
+    ip = None
+    regs = [0 for _ in range(6)]
+    regs[0] = reg_zero_init
+
+    insts = []
+    for line in data.splitlines():
+        if line.startswith("#"):
+            (ip,) = str_to_ints(line)
+        else:
+            fs = line.split()
+            vals = str_to_ints(line)
+            insts.append([fs[0]] + vals)
+
+    count = 0
+    assert ip is not None
+    while regs[ip] < len(insts):
+        if break_after is not None and count > break_after:
+            break
+        inst = insts[regs[ip]]
+        f = getattr(d16, inst[0])
+        f(regs, *inst[1:])
+        regs[ip] += 1
+        count += 1
+    return regs
+
+
+def part_1(data):
+    regs = run(data)
+    print(regs[0])
+
+
+def part_2(data):
+    regs = run(data, 10_000, 1)
+    # by analysing the code we can see that the int computer counts the sum of
+    # the number of divisors
+    print(sum_of_divisors(regs[1]))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()
+
+
+listing = """
+ip=5
+ 0 ip = regs[5] + 16
+ 1 regs[2] = 1
+ 2 regs[4] = 1
+ 3 regs[3] = regs[2] * regs[4]              |
+ 4 regs[3] = (regs[3] == regs[1]) ? 1 : 0   |
+ 5 ip = regs[3] + regs[5]                   | jump to 7 if regs[3] == regs[1]
+ 6 ip = regs[5] + 1                         | skip 7
+ 7 regs[0] = regs[2] + regs[0]
+ 8 regs[4] = regs[4] + 1                    | regs[4] += 1
+ 9 regs[3] = (regs[4] > regs[1]) ? 1 : 0    |
+10 ip = regs[5] + regs[3]                   | jump to 12 if regs[4] > regs[1]
+11 ip = 2                                   | goto 3
+12 regs[2] = regs[2] + 1                    | regs[2] += 1
+13 regs[3] = (regs[2] > regs[1]) ? 1 : 0    | 
+14 ip = regs[3] + regs[5]                   | jump to 16 if regs[2] > regs[1]
+15 ip = 1                                   | goto 2
+16 ip = regs[5] * regs[5]
+17 regs[1] = regs[1] + 2
+18 regs[1] = regs[1] * regs[1]
+19 regs[1] = regs[5] * regs[1]
+20 regs[1] = regs[1] * 11
+21 regs[3] = regs[3] + 6
+22 regs[3] = regs[3] * regs[5]
+23 regs[3] = regs[3] + 15
+24 regs[1] = regs[1] + regs[3]
+25 ip = regs[5] + regs[0]
+26 ip = 0
+27 regs[3] = regs[5]
+28 regs[3] = regs[3] * regs[5]
+29 regs[3] = regs[5] + regs[3]
+30 regs[3] = regs[5] * regs[3]
+31 regs[3] = regs[3] * 14
+32 regs[3] = regs[3] * regs[5]
+33 regs[1] = regs[1] + regs[3]
+34 regs[0] = 0
+35 ip = 0
+
+hypothesis: usm of numbers that divide the number in regs[0]
+"""

2018/d20.py

@@ -0,0 +1,94 @@
+from lib import get_data, add2
+from collections import defaultdict
+
+DIRS = {
+    "N": (-1, 0),
+    "E": (0, 1),
+    "S": (1, 0),
+    "W": (0, -1),
+}
+
+data = get_data(__file__).strip()
+g = defaultdict(set)
+seen = set()
+stack: list[tuple[tuple, int, list]] = [((0, 0), 0, [])]
+while len(stack) > 0:
+    pos, i, i_outs = stack.pop()
+
+    c = (pos, i, tuple(i_outs))
+    if c in seen:
+        continue
+    else:
+        seen.add(c)
+
+    assert i is not None
+    while i < len(data):
+        c = data[i]
+        if c in DIRS.keys():
+            npos = add2(pos, DIRS[c])
+            g[pos].add(npos)
+            g[npos].add(pos)
+            pos = npos
+            i += 1
+        elif c == "(":
+            to_continue = [i + 1]
+            open_count = 0
+            j_out = None
+            for j in range(i + 1, len(data)):
+                c = data[j]
+                if c == "|" and open_count == 0:
+                    to_continue.append(j + 1)
+                elif c == "(":
+                    open_count += 1
+                elif c == ")" and open_count != 0:
+                    open_count -= 1
+                elif c == ")" and open_count == 0:
+                    j_out = j
+                    break
+            assert j_out is not None
+
+            for new_i in to_continue:
+                new_i_outs = list(i_outs)
+                new_i_outs.append(j_out)
+                stack.append((pos, new_i, new_i_outs))
+            break
+        elif c == "$":
+            break
+        elif c == ")" and len(i_outs) == 0:
+            assert False, "Encountered | without i_out"
+        elif c == ")":
+            i_new = i_outs.pop()
+            assert i == i_new
+            i += 1
+        elif c == "^":
+            i += 1
+        elif c == "|" and len(i_outs) == 0:
+            assert False, "Encountered | without i_out"
+        elif c == "|":
+            i = i_outs.pop()
+            i += 1
+        else:
+            assert False
+
+seen = set()
+dists = {}
+xs = [(0, 0)]
+steps = 0
+over_thousand = set()
+while len(xs) > 0:
+    nxs = []
+    for x in xs:
+        if x in seen:
+            continue
+        if steps >= 1000:
+            over_thousand.add(x)
+        seen.add(x)
+        dists[x] = steps
+        for nb in g[x]:
+            if not nb in seen:
+                nxs.append(nb)
+    xs = nxs
+    steps += 1
+
+print(max(dists.values()))
+print(len(over_thousand))

2018/d21.py

@@ -0,0 +1,52 @@
+from lib import get_data, str_to_ints
+import d16
+
+
+def run(data, break_after=None, reg_zero_init=0):
+    ip = None
+    regs = [0 for _ in range(6)]
+    regs[0] = reg_zero_init
+
+    insts = []
+    for line in data.splitlines():
+        if line.startswith("#"):
+            (ip,) = str_to_ints(line)
+        else:
+            fs = line.split()
+            vals = str_to_ints(line)
+            insts.append([fs[0]] + vals)
+
+    count = 0
+    assert ip is not None
+    seen = set()
+    last_added = None
+    while regs[ip] < len(insts):
+        if break_after is not None and count > break_after:
+            break
+        if regs[ip] == 28:
+            r4 = regs[4]
+
+            if len(seen) == 0:
+                print(r4)
+
+            if r4 in seen:
+                print(last_added)
+                break
+            else:
+                seen.add(r4)
+                last_added = r4
+
+        inst = insts[regs[ip]]
+        f = getattr(d16, inst[0])
+        f(regs, *inst[1:])
+        regs[ip] += 1
+        count += 1
+
+
+def main():
+    data = get_data(__file__)
+    run(data, reg_zero_init=333)
+
+
+if __name__ == "__main__":
+    main()

2018/d22.py

@@ -0,0 +1,89 @@
+from lib import get_data, str_to_ints, A_Star
+
+data = get_data(__file__)
+
+depth, x_target, y_target = str_to_ints(data)
+# depth, x_target, y_target = 510, 10, 10
+# depth, x_target, y_target = 9171, 7, 721
+# print(depth, x_target, y_target)
+
+x_area_max = x_target * 10
+y_area_max = y_target * 10
+
+maze = [[None for _ in range(x_area_max + 1)] for _ in range(y_area_max + 1)]
+
+maze[0][0] = 0
+maze[y_target][x_target] = 0
+
+mod = 20183
+for x in range(x_area_max + 1):
+    maze[0][x] = x * 16807 % mod
+
+for y in range(y_area_max + 1):
+    maze[y][0] = y * 48271 % mod
+
+for y in range(1, y_area_max + 1):
+    for x in range(1, x_area_max + 1):
+        if x == x_target and y == y_target:
+            continue
+        assert maze[y][x] is None
+        geo_index = ((maze[y][x - 1] + depth) * (maze[y - 1][x] + depth)) % mod
+        maze[y][x] = geo_index
+
+t = 0
+for y in range(y_target + 1):
+    for x in range(x_target + 1):
+        t += ((maze[y][x] + depth) % mod) % 3
+print(t)
+
+for y in range(y_area_max + 1):
+    for x in range(x_area_max + 1):
+        maze[y][x] = ((maze[y][x] + depth) % mod) % 3
+
+
+def allowed(area, tool):
+    # 0 = rocky, 1 = wet, 2 = narrow
+    # 0 = torch, 1 = climbing, 2 = neither
+    return (
+        (area == 0 and (tool in [0, 1]))
+        or (area == 1 and (tool in [1, 2]))
+        or (area == 2 and (tool in [0, 2]))
+    )
+
+
+def neighbors(state):
+    x, y, tool = state
+    r = []
+    area = maze[y][x]
+    for t in range(3):
+        if allowed(area, t) and t != tool:
+            r.append((x, y, t))
+
+    for dx, dy in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
+        nx, ny = x + dx, y + dy
+        if not (nx >= 0 and nx < x_area_max and ny >= 0 and ny < y_area_max):
+            continue
+        if not allowed(maze[ny][nx], tool):
+            continue
+        r.append((nx, ny, tool))
+    return r
+
+
+def distance(a, b):
+    if a == 0:
+        return 0
+    elif a[2] != b[2]:
+        assert a[0] == b[0] and a[1] == b[1]
+        return 7
+    else:
+        return 1
+
+
+a = A_Star(
+    starts=[(0, 0, 0)],
+    is_goal=lambda s: s[0] == x_target and s[1] == y_target and s[2] == 0,
+    h=lambda s: abs(s[0] - x_target) + abs(s[1] - y_target),
+    d=distance,
+    neighbors=neighbors,
+)
+print(a.cost)

2018/d23.py

@@ -0,0 +1,45 @@
+from lib import get_data, ints
+
+data = get_data(__file__)
+
+X, Y, Z, RADIUS = 0, 1, 2, 3
+
+
+def dist(a, b):
+    return sum(abs(x - y) for x, y in zip(a[:RADIUS], b[:RADIUS]))
+
+
+bots = [ints(line) for line in data.splitlines()]
+max_bot = max(bots, key=lambda b: b[RADIUS])
+r = max_bot[3]
+t = sum(1 for bot in bots if dist(bot, max_bot) <= r)
+print(t)
+
+from z3 import Int, If, Abs, Sum, IntVal, Optimize, set_param
+
+
+x = Int("x")
+y = Int("y")
+z = Int("z")
+
+z3zero = IntVal(0)
+z3one = IntVal(1)
+n_out_of_range = Int("n_out_of_range")
+dist_origin = Int("dist_origin")
+
+bots_out_of_range = [
+    If(Abs(b[X] - x) + Abs(b[Y] - y) + Abs(b[Z] - z) > b[RADIUS], z3one, z3zero)
+    for b in bots
+]
+
+set_param("parallel.enable", True)
+
+opt = Optimize()
+opt.add(n_out_of_range == Sum(bots_out_of_range))
+opt.add(dist_origin == Abs(x) + Abs(y) + Abs(z))
+opt.minimize(n_out_of_range)
+opt.minimize(dist_origin)
+
+res = opt.check()
+m = opt.model()
+print(m[dist_origin])

2018/d24.py

@@ -0,0 +1,179 @@
+import re
+from lib import get_data, ints
+from collections import defaultdict
+from copy import deepcopy
+
+r = re.compile(r"(immune|weak) to ([\w ,]+)")
+r_strength = re.compile(r"(\w+) damage")
+
+data = """Immune System:
+17 units each with 5390 hit points (weak to radiation, bludgeoning) with an attack that does 4507 fire damage at initiative 2
+989 units each with 1274 hit points (immune to fire; weak to bludgeoning, slashing) with an attack that does 25 slashing damage at initiative 3
+
+Infection:
+801 units each with 4706 hit points (weak to radiation) with an attack that does 116 bludgeoning damage at initiative 1
+4485 units each with 2961 hit points (immune to radiation; weak to fire, cold) with an attack that does 12 slashing damage at initiative 4
+ """
+data = get_data(__file__)
+
+ARMY, ID, UNITS, HITS, DAMG, INIT = 0, 1, 2, 3, 4, 5
+
+groups = []
+unit_meta = {}
+
+id = 1
+for a, p in enumerate(data.split("\n\n")):
+    for line in p.splitlines():
+        xs = ints(line)
+        if len(xs) == 0:
+            continue
+        assert len(xs) == 4
+        xs = [a, id] + xs
+
+        (attack,) = r_strength.findall(line)
+        defense = defaultdict(list)
+        for attr, values in r.findall(line):
+            defense[attr] = values.split(", ")
+
+        unit_meta[id] = attack, defense
+        groups.append(xs)
+        id += 1
+
+
+def effective_power(group):
+    return (group[UNITS] * group[DAMG], group[INIT])
+
+
+def damage(g1, g2):
+    """Damage g1 does to g2"""
+    g1_id, g2_id = g1[ID], g2[ID]
+    g1_attack_type = unit_meta[g1_id][0]
+    g2_defenses = unit_meta[g2_id][1]
+    g2_immune = True if g1_attack_type in g2_defenses["immune"] else False
+    g2_weak = True if g1_attack_type in g2_defenses["weak"] else False
+
+    assert (g2_immune and g2_weak) != True
+
+    damage = g1[UNITS] * g1[DAMG]
+    if g2_immune:
+        damage = 0
+    elif g2_weak:
+        damage *= 2
+    return damage
+
+
+groups_orig = deepcopy(groups)
+while True:
+    groups = sorted(groups, key=effective_power, reverse=True)
+    attacks = {}
+    attacked = set()
+    for g in groups:
+        target_max_stats = 0, 0, 0
+        target = None
+        for t in groups:
+            if g[ARMY] == t[ARMY]:
+                continue
+            if g[ID] == t[ID]:
+                continue
+            if t[ID] in attacked:
+                continue
+            target_stats = damage(g, t), effective_power(t)[0], t[INIT]
+            if target_stats[0] == 0:
+                continue
+            if target_stats > target_max_stats:
+                target_max_stats = target_stats
+                target = t
+
+        if target is not None:
+            attacked.add(target[ID])
+            attacks[g[ID]] = target
+
+    groups = sorted(groups, key=lambda g: g[INIT], reverse=True)
+    for g in groups:
+        if g[ID] not in attacks:
+            continue
+        if g[UNITS] <= 0:
+            continue
+
+        target = attacks[g[ID]]
+        cdamage = damage(g, target)
+        units_dead = cdamage // target[HITS]
+        units_dead = units_dead if units_dead <= target[UNITS] else target[UNITS]
+        # print("immune" if g[ARMY] == 0 else "infection", g[ID], "attacks", target[ID], "dead", units_dead)
+        target[UNITS] -= units_dead
+
+    groups = [g for g in groups if g[UNITS] > 0]
+    armies = set()
+    for g in groups:
+        armies.add(g[ARMY])
+    assert len(armies) >= 1
+    if len(armies) == 1:
+        break
+
+
+t = sum(g[UNITS] for g in groups)
+print(t)
+
+
+for boost in range(0, 1800):
+    groups = deepcopy(groups_orig)
+    for g in groups:
+        if g[ARMY] == 0:
+            g[DAMG] += boost
+
+    while True:
+        groups = sorted(groups, key=effective_power, reverse=True)
+        attacks = {}
+        attacked = set()
+        for g in groups:
+            target_max_stats = 0, 0, 0
+            target = None
+            for t in groups:
+                if g[ARMY] == t[ARMY]:
+                    continue
+                if g[ID] == t[ID]:
+                    continue
+                if t[ID] in attacked:
+                    continue
+                target_stats = damage(g, t), effective_power(t)[0], t[INIT]
+                if target_stats[0] == 0:
+                    continue
+                if target_stats > target_max_stats:
+                    target_max_stats = target_stats
+                    target = t
+
+            if target is not None:
+                attacked.add(target[ID])
+                attacks[g[ID]] = target
+
+        groups = sorted(groups, key=lambda g: g[INIT], reverse=True)
+        max_dead = 0
+        for g in groups:
+            if g[ID] not in attacks:
+                continue
+            if g[UNITS] <= 0:
+                continue
+
+            target = attacks[g[ID]]
+            cdamage = damage(g, target)
+            units_dead = cdamage // target[HITS]
+            units_dead = units_dead if units_dead <= target[UNITS] else target[UNITS]
+            max_dead = max(units_dead, max_dead)
+            # print("immune" if g[ARMY] == 0 else "infection", g[ID], "attacks", target[ID], "dead", units_dead)
+            target[UNITS] -= units_dead
+
+        if max_dead == 0:
+            break
+
+        groups = [g for g in groups if g[UNITS] > 0]
+        armies = set()
+        for g in groups:
+            armies.add(g[ARMY])
+        assert len(armies) >= 1
+        if len(armies) == 1:
+            army = groups[0][ARMY]
+            t = sum(g[UNITS] for g in groups)
+            if army == 0:
+                print(t)
+                exit(0)
+            break

2018/d25.py

@@ -0,0 +1,38 @@
+from lib import get_data, ints
+
+
+def mdist(x, y):
+    return sum(abs(a - b) for a, b in zip(x, y))
+
+
+data = get_data(__file__)
+xss = [tuple(ints(line)) for line in data.splitlines()]
+
+# check if we can use set (even though we didn't end up using sets)
+assert len(xss) == len(set(xss))
+
+unplaced = list(xss)
+groups = [[unplaced.pop()]]
+while unplaced:
+    # see if any start fits into the current group
+    current_group = groups[-1]
+    add = None
+    for u in unplaced:
+        for x in current_group:
+            if mdist(u, x) <= 3:
+                add = u
+                break
+        if add is not None:
+            break
+
+    if add is not None:
+        # if yes, add the start to that group and see if another one can be
+        # added to the same group
+        unplaced.remove(add)
+        current_group.append(add)
+    else:
+        # if no, create a new group with an unplaced start
+        groups.append([unplaced.pop()])
+
+
+print(len(groups))

2018/d9.py

@@ -0,0 +1,73 @@
+from lib import str_to_ints
+from collections import defaultdict
+
+
+def part_1(data):
+    scores = defaultdict(int)
+    n_players, worth = str_to_ints(data)
+    current_player = 0
+    circle = [0]
+    current = 1
+    for n in range(1, worth + 1):
+        if n % 23 == 0:
+            scores[current_player] += n
+            current = (current - 7) % len(circle)
+            scores[current_player] += circle.pop(current)
+        else:
+            current = (current + 2) % len(circle)
+            circle.insert(current, n)
+        current_player = (current_player + 1) % n_players
+    print(max(scores.values()))
+
+
+class Node:
+    def __init__(self, value, prev=None, next=None):
+        self.value = value
+        if prev is None:
+            self.prev = self
+        else:
+            self.prev = prev
+        if next is None:
+            self.next = self
+        else:
+            self.next = next
+
+
+def part_2(data):
+    scores = defaultdict(int)
+    n_players, worth = str_to_ints(data)
+    current_player = 0
+    first = Node(0)
+    current = first
+    current.next = current
+    current.prev = current
+
+    for n in range(1, (worth * 100) + 1):
+        if n % 23 == 0:
+            scores[current_player] += n
+            for _ in range(7):
+                current = current.prev
+            scores[current_player] += current.value
+            current.prev.next = current.next
+            current.next.prev = current.prev
+            current = current.next
+        else:
+            new_current = Node(n, current.next, current.next.next)
+            current.next.next.prev = new_current
+            current.next.next = new_current
+            current = new_current
+        current_player = (current_player + 1) % n_players
+
+    print(max(scores.values()))
+
+
+def main():
+    input_file = __file__.replace(".py", ".txt")
+    with open(input_file) as f:
+        data = f.read()
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2018/monitor.py

@@ -0,0 +1 @@
+../monitor.py

2019/d1.py

@@ -0,0 +1,31 @@
+from lib import get_data
+
+
+def f(i):
+    i //= 3
+    i -= 2
+    return i
+
+
+def part_1(data):
+    print(sum([f(int(line)) for line in data.splitlines()]))
+
+
+def part_2(data):
+    r = 0
+    for line in data.splitlines():
+        i = f(int(line))
+        while i > 0:
+            r += i
+            i = f(i)
+    print(r)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d10.py

@@ -0,0 +1,102 @@
+from lib import get_data, Grid2D
+from math import gcd, atan2, pi
+
+
+def angle(a1, a2):
+    dy = a1[0] - a2[0]
+    dx = a2[1] - a1[1]
+    a = (atan2(dx, dy) + 2 * pi) % (2 * pi)
+    return a
+
+
+def dist(a1, a2):
+    return abs(a1[0] - a2[0]) + abs(a1[1] - a2[1])
+
+
+def part_1(data):
+    g = Grid2D(data)
+    asts = g.find("#")
+    asts_set = set(asts)
+
+    best_ast = None
+    visible_max = 0
+    for a in asts:
+        visible = 0
+        for other in asts:
+            if a == other:
+                continue
+            x1, x2 = a[0], other[0]
+            y1, y2 = a[1], other[1]
+
+            if y1 == y2:
+                for x in range(min(x1, x2) + 1, max(x1, x2)):
+                    if (x, y1) in asts_set:
+                        break
+                else:
+                    visible += 1
+            elif x1 == x2:
+                for y in range(min(y1, y2) + 1, max(y1, y2)):
+                    if (x1, y) in asts_set:
+                        break
+                else:
+                    visible += 1
+            else:
+                dx = abs(x1 - x2)
+                dy = abs(y1 - y2)
+                g = gcd(dx, dy)
+                dx //= g
+                dy //= g
+
+                x, y = x1, y1
+                if x2 < x1:
+                    dx = -dx
+                if y2 < y1:
+                    dy = -dy
+
+                blocked = False
+                while True:
+                    x += dx
+                    y += dy
+                    if (x, y) == (x2, y2):
+                        break
+                    if (x, y) in asts_set:
+                        blocked = True
+                        break
+                if not blocked:
+                    visible += 1
+
+        if visible > visible_max:
+            visible_max = visible
+            best_ast = a
+
+    assert best_ast is not None
+    print(visible_max)
+
+    other_asts = [a for a in asts if a != best_ast]
+    removed_count = 0
+    while True:
+        removed = set()
+        other_asts = sorted(
+            other_asts, key=lambda a: (angle(best_ast, a), dist(best_ast, a))
+        )
+        lowest_angle = -1
+        for a in other_asts:
+            current_angle = angle(best_ast, a)
+            if current_angle > lowest_angle:
+                removed.add(a)
+                lowest_angle = current_angle
+                removed_count += 1
+
+            if removed_count == 200:
+                print(a[1] * 100 + a[0])
+                return
+        other_asts = [a for a in other_asts if a not in removed]
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d11.py

@@ -0,0 +1,93 @@
+from lib import get_data, str_to_ints, add2
+from d9 import Amp
+
+DIRS = [(-1, 0), (0, 1), (1, 0), (0, -1)]
+BLACK = 0
+WHITE = 1
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    a = Amp(xs)
+    current_dir_idx = 0
+    pos = (0, 0)
+    white_panels = set()
+    got_painted = set()
+
+    while not a.done:
+        if pos in white_panels:
+            a.feed(WHITE)
+        else:
+            a.feed(BLACK)
+        a.go()
+        a.go()
+        while a.outputs:
+            paint_color = a.pop()
+            if paint_color == BLACK:
+                white_panels.remove(pos)
+            elif paint_color == WHITE:
+                white_panels.add(pos)
+            else:
+                assert False
+            got_painted.add(pos)
+            turn_dir_code = a.pop()
+            turn_dir = -1 if turn_dir_code == 0 else 1
+            current_dir_idx = (current_dir_idx + turn_dir) % len(DIRS)
+            pos = add2(pos, DIRS[current_dir_idx])
+    print(len(got_painted))
+
+
+def part_2(data):
+    xs = str_to_ints(data)
+    a = Amp(xs)
+    current_dir_idx = 0
+    pos = (0, 0)
+    white_panels = set([pos])
+    got_painted = set()
+
+    while not a.done:
+        if pos in white_panels:
+            a.feed(WHITE)
+        else:
+            a.feed(BLACK)
+        a.go()
+        a.go()
+        while a.outputs:
+            paint_color = a.pop()
+            if paint_color == BLACK:
+                if pos in white_panels:
+                    white_panels.remove(pos)
+            elif paint_color == WHITE:
+                white_panels.add(pos)
+            else:
+                assert False
+            got_painted.add(pos)
+            turn_dir_code = a.pop()
+            turn_dir = -1 if turn_dir_code == 0 else 1
+            current_dir_idx = (current_dir_idx + turn_dir) % len(DIRS)
+            pos = add2(pos, DIRS[current_dir_idx])
+
+    white_panels = [(p[1], p[0]) for p in white_panels]
+    xs = [p[0] for p in white_panels]
+    ys = [p[1] for p in white_panels]
+    white_panels_set = set(white_panels)
+    x_min, x_max = min(xs), max(xs)
+    y_min, y_max = min(ys), max(ys)
+    for y in range(y_min, y_max + 1):
+        s = ""
+        for x in range(x_min, x_max + 1):
+            if (x, y) in white_panels_set:
+                s += "X"
+            else:
+                s += " "
+        print(s)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d12.py

@@ -0,0 +1,87 @@
+from lib import get_data, str_to_ints
+from math import lcm
+
+
+def freeze(coords, velos):
+    coords = tuple(map(tuple, coords))
+    velos = tuple(map(tuple, velos))
+    return coords + velos
+
+
+def part_1(data):
+    coords = []
+    velos = []
+    for line in data.splitlines():
+        coords.append(str_to_ints(line))
+        velos.append([0, 0, 0])
+
+    for _ in range(1_000):
+        # apply gravity
+        for i in range(len(coords)):
+            for j in range(i + 1, len(coords)):
+                for d in range(3):
+                    if coords[i][d] > coords[j][d]:
+                        velos[i][d] -= 1
+                        velos[j][d] += 1
+                    elif coords[i][d] < coords[j][d]:
+                        velos[i][d] += 1
+                        velos[j][d] -= 1
+
+        # update coords
+        for i in range(len(coords)):
+            for d in range(3):
+                coords[i][d] += velos[i][d]
+
+    r = 0
+    for i in range(len(coords)):
+        p = sum(map(abs, coords[i]))
+        k = sum(map(abs, velos[i]))
+        r += p * k
+    print(r)
+
+
+def part_2(data):
+    steps = []
+    for i in range(3):
+        coords = []
+        velos = []
+
+        for line in data.splitlines():
+            coords.append(str_to_ints(line)[i])
+            velos.append(0)
+
+        seen = {}
+        for step in range(1_000_000):
+            state = tuple(coords) + tuple(velos)
+            if state in seen:
+                steps.append(step)
+                break
+            else:
+                seen[state] = step
+
+            for i in range(len(coords)):
+                for j in range(i + 1, len(coords)):
+                    if coords[i] > coords[j]:
+                        velos[i] -= 1
+                        velos[j] += 1
+                    elif coords[i] < coords[j]:
+                        velos[i] += 1
+                        velos[j] -= 1
+
+            # update coords
+            for i in range(len(coords)):
+                coords[i] += velos[i]
+
+    # Intuition: Find when position repeats on each axis and then find lowest
+    # common multiple for all three values.
+    print(lcm(*steps))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d13.py

@@ -0,0 +1,50 @@
+from lib import get_data, str_to_ints
+from d9 import Amp
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    a = Amp(xs)
+    while not a.done:
+        a.go()
+
+    r = sum([a.outputs[i : i + 3][2] == 2 for i in range(0, len(a.outputs), 3)])
+    print(r)
+
+
+def part_2(data):
+    xs = str_to_ints(data)
+    xs[0] = 2  # play for free
+    a = Amp(xs)
+    ball_x = 0
+    paddle_x = 0
+    score = 0
+    while not a.done:
+        a.go()
+        if len(a.outputs) == 3:
+            x, y, tile_id = a.pop(), a.pop(), a.pop()
+            if x == -1 and y == 0:
+                score = tile_id
+            elif tile_id == 4:
+                ball_x = x
+            elif tile_id == 3:
+                paddle_x = x
+        if a.input_required:
+            a.input_required = False
+            x = 0
+            if ball_x < paddle_x:
+                x = -1
+            elif ball_x > paddle_x:
+                x = 1
+            a.feed(x)
+    print(score)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d14.py

@@ -0,0 +1,83 @@
+from lib import get_data
+from math import ceil
+
+
+def ore_for_fuel(fuel_n, reactions_store):
+    ore_qty = 0
+    required = [(fuel_n, "FUEL")]
+    store = {}
+    while required:
+        required_qty, required_code = required.pop()
+        if required_code == "ORE":
+            ore_qty += required_qty
+            continue
+
+        if required_code in store:
+            if store[required_code] == required_qty:
+                del store[required_code]
+                continue
+            elif store[required_code] > required_qty:
+                store[required_code] -= required_qty
+                continue
+            elif store[required_code] < required_qty:
+                required_qty -= store[required_code]
+                del store[required_code]
+
+        inputs, output = reactions_store[required_code]
+        output_qty, output_code = output
+        assert required_code == output_code
+
+        # how often must this process be executed
+        n = ceil(required_qty / output_qty)
+
+        leftover_output_qty = n * output_qty - required_qty
+        assert leftover_output_qty >= 0
+
+        if leftover_output_qty > 0:
+            store[output_code] = leftover_output_qty
+
+        for qty_input, input_code in inputs:
+            required.append((qty_input * n, input_code))
+    return ore_qty
+
+
+def part_1(data):
+    reactions = []
+    to_get = {}
+    for line in data.splitlines():
+        left, right = line.split(" => ")
+        inputs = left.split(", ")
+        inputs = [(int(i.split()[0]), i.split()[1]) for i in inputs]
+        output = (int(right.split()[0]), right.split()[1])
+        reactions.append((inputs, output))
+        if output[1] in to_get:
+            assert False
+        else:
+            to_get[output[1]] = (inputs, output)
+
+    ore_qty = ore_for_fuel(1, to_get)
+    print(ore_qty)
+
+    min_fuel, max_fuel = 1, 100_000_000
+    target = 10**12  # trillion
+    while max_fuel - min_fuel > 1:
+        half_fuel = min_fuel + (max_fuel - min_fuel) // 2
+        ore_qty = ore_for_fuel(half_fuel, to_get)
+        if ore_qty < target:
+            min_fuel = half_fuel
+        elif ore_qty > target:
+            max_fuel = half_fuel
+        else:
+            min_fuel = half_fuel
+            max_fuel = half_fuel
+
+    print(min_fuel)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d15.py

@@ -0,0 +1,115 @@
+from lib import get_data, str_to_ints, add2
+from d9 import Amp
+
+
+DIRS = {1: (-1, 0), 2: (1, 0), 3: (0, -1), 4: (0, 1)}
+PATH_REVERSED = {1: 2, 2: 1, 3: 4, 4: 3}
+
+
+def print_field(fields, walls, pos):
+    dim = 40
+    for y in range(-dim, dim + 1):
+        row = ""
+        for x in range(-dim, dim + 1):
+            if (y, x) == pos:
+                row += "X"
+            elif (y, x) in fields:
+                row += "."
+            elif (y, x) in walls:
+                row += "|"
+            else:
+                row += " "
+        print(row)
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    a = Amp(xs)
+
+    walls = set()
+    pos = (0, 0)
+    target = None
+    dir = None
+    path = []
+    dir_cmds_for_pos = {pos: [1, 2, 3, 4]}
+
+    while not a.done:
+        if len(dir_cmds_for_pos[pos]) > 0:
+            dir_cmd = dir_cmds_for_pos[pos].pop()
+            dir = DIRS[dir_cmd]
+
+            new_pos = add2(pos, dir)
+            if new_pos in dir_cmds_for_pos:
+                continue
+
+            a.feed(dir_cmd)
+            a.go()
+            status = a.pop()
+
+            if status == 0:
+                walls.add(new_pos)
+            elif status == 1:
+                pos = new_pos
+                path.append(dir_cmd)
+            elif status == 2:
+                pos = new_pos
+                path.append(dir_cmd)
+                target = pos
+
+            if pos not in dir_cmds_for_pos:
+                dir_cmds_for_pos[pos] = [1, 2, 3, 4]
+
+        elif len(path) > 0:
+            dir_cmd = PATH_REVERSED[path.pop()]
+            dir = DIRS[dir_cmd]
+            pos = add2(pos, dir)
+            a.feed(dir_cmd)
+            a.go()
+            status = a.pop()
+            assert status == 1 or status == 2
+        elif target is not None:
+            break
+        else:
+            break
+    fields = set(dir_cmds_for_pos.keys())
+    # print_field(fields, walls, pos)
+
+    seen = set()
+    to_visit = [(0, 0)]
+    steps = 0
+    while len(to_visit) > 0:
+        new = []
+        for current in to_visit:
+            if current == target:
+                print(steps)
+            seen.add(current)
+            for dir in DIRS.values():
+                nb = add2(current, dir)
+                if nb in fields and nb not in seen:
+                    new.append(nb)
+        to_visit = new
+        steps += 1
+
+    seen = set()
+    to_visit = [target]
+    steps = 0
+    while len(to_visit) > 0:
+        new = []
+        for current in to_visit:
+            seen.add(current)
+            for dir in DIRS.values():
+                nb = add2(current, dir)
+                if nb in fields and nb not in seen:
+                    new.append(nb)
+        to_visit = new
+        steps += 1
+    print(steps - 1)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d16.py

@@ -0,0 +1,132 @@
+from lib import get_data
+
+
+def part_1_with_numpy(data):
+    import numpy as np
+
+    def make_base_matrix(pattern, n):
+        xss = []
+        for round in range(n):
+            xs = [pattern[((i + 1) // (round + 1)) % len(pattern)] for i in range(n)]
+            xss.append(xs)
+        return np.array(xss)
+
+    pattern = [0, 1, 0, -1]
+    input = int(data.strip())
+    v = np.array(list(map(int, str(input))))
+    m = make_base_matrix(pattern, len(v))
+    func = np.vectorize(lambda x: abs(x) % 10)
+
+    for _ in range(100):
+        v = func(np.dot(m, v))
+    print("".join(map(str, v[:8].tolist())))
+
+
+def phase(digits_in):
+    pattern = [0, 1, 0, -1]
+    digits_out = []
+    for round in range(len(digits_in)):
+        i, out = 0, 0
+        while i < len(digits_in):
+            pattern_i = ((i + 1) // (round + 1)) % len(pattern)
+            out += pattern[pattern_i] * digits_in[i]
+            i += 1
+        out = abs(out) % 10
+        digits_out.append(out)
+    return digits_out
+
+
+def phase_with_offset(digits_in, pattern, offset):
+    digits_out = digits_in.copy()
+    for round in range(offset, len(digits_in)):
+        i, out = 0, 0
+        # print(round)
+
+        pattern_value = pattern[((i + 1) // (round + 1)) % len(pattern)]
+        if pattern_value == 0:
+            i += round
+
+        while i < len(digits_in):
+            pattern_i = ((i + 1) // (round + 1)) % len(pattern)
+            pattern_value = pattern[pattern_i]
+            if pattern_value != 0:
+                out += pattern_value * sum(
+                    digits_in[i : min(i + 1 + round, len(digits_in))]
+                )
+            i += round + 1
+
+        out = abs(out) % 10
+        digits_out[round] = out
+
+    return digits_out
+
+
+def part_1(data):
+    pattern = [0, 1, 0, -1]
+
+    input = list(map(int, (data.strip())))
+    for _ in range(100):
+        input = phase_with_offset(input, pattern, 0)
+    print("".join(map(str, input[:8])))
+
+    out = list(map(int, (data.strip()))) * 10_000
+    offset = int("".join(map(str, out[:7])))
+    for _ in range(100):
+        for i in range(len(out) - 2, len(out) - 1_000_000, -1):
+            out[i] = abs(out[i] + out[i + 1]) % 10
+    print("".join(map(str, out[offset : offset + 8])))
+
+    # digits = 40
+    # for round in range(digits):
+    #     s = ""
+    #     for i in range(digits):
+    #         pattern_i = ((i + 1) // (round + 1)) % len(pattern)
+    #         pattern_value = pattern[pattern_i]
+    #         if pattern_value == 0:
+    #             s += " "
+    #         elif pattern_value == 1:
+    #             s += "+"
+    #         elif pattern_value == -1:
+    #             s += "-"
+    #         else:
+    #             assert False
+    #     print(s)
+    # return
+
+    # Just here to document my thought process. Mental hack: Assume that you
+    # have the capability to solve the problem easily.
+    #
+    # What do I know?
+    #
+    # 1. There is a solution. Other people have solved it.
+    # 2. The solution is not crazy. It will be rather obvious.
+    # 3. 6_500_000 * 6_500_000 is definitely too much to brute force.
+    # 4. Can we go from O(N^2) to O(N) somehow? Yes, that's what we have to do.
+    #    The whole point of FFT is to get from O(N^2) to O(N*log(N)). Now,
+    #    how exactly do we do that?
+    #
+    # Ways to improve performance:
+    #
+    # 1. Speed up `phase` significantly. Yes, but how?
+    # 2. Only compute a subset of the lists? - No!
+    # 3. Discover some kind of pattern? - No!
+    #
+    # Assumptions:
+    #
+    # 1. I need every digit of the previous round. - False!
+    # 2. I cannot just operate on a subset. - False!
+    #
+    # Non-approaches:
+    #
+    # 1. Fancy recursive algorithm that selectively picks fields.
+    # 2. Pattern detection or subset consideration.
+
+
+def main():
+    data = get_data(__file__)
+    # part_1_with_numpy(data)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d17.py

@@ -0,0 +1,136 @@
+from lib import get_data, str_to_ints, Grid2D, add2
+from collections import defaultdict
+from d9 import Amp
+
+DIRS = [
+    (-1, 0),
+    (0, 1),
+    (1, 0),
+    (0, -1),
+]
+
+DIRCHAR = list("^>v<")
+
+
+def find_path(g):
+    (pos,) = g.find("^><v")
+    assert g[pos] == "^"
+
+    to_visit = set(g.find("#"))
+    seen = defaultdict(int)
+    dir = DIRS[0]  # up
+    seen[pos] = 1
+
+    def best_neighbor(pos):
+        best_nb = None
+        seen_count = 20
+        for nb in g.neighbors_ort(pos):
+            if nb in to_visit:
+                return nb
+            if nb in seen and seen[nb] < seen_count:
+                seen_count = seen[nb]
+                best_nb = nb
+        assert best_nb is not None
+        return best_nb
+
+    path = ""
+    while to_visit:
+
+        new_pos = add2(pos, dir)
+        if new_pos in to_visit or (new_pos in seen and seen[new_pos] < 2):
+            path += "F"
+            g[pos] = "#"
+            pos = new_pos
+            if pos in to_visit:
+                to_visit.remove(pos)
+            g[pos] = DIRCHAR[DIRS.index(dir)]
+            seen[pos] += 1
+        else:
+            best_nb = best_neighbor(pos)
+            while add2(pos, dir) != best_nb:
+                path += "R"
+                dir = DIRS[(DIRS.index(dir) + 1) % len(DIRS)]
+                g[pos] = DIRCHAR[DIRS.index(dir)]
+
+        # For debugging:
+        # g.print()
+        # input()
+        # print()
+    path = path.replace("RRR", "L")
+    return path
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    a = Amp(xs)
+    text = ""
+    while not a.done:
+        a.go()
+        while a.outputs:
+            o = a.pop()
+            text += chr(o)
+
+    result = 0
+    g = Grid2D(text)
+    for r in range(g.n_rows):
+        for c in range(g.n_cols):
+            nbs = g.neighbors_ort((r, c))
+            if (
+                g[(r, c)] == "#"
+                and len(nbs) == 4
+                and all([g[(nr, nc)] == "#" for nr, nc in nbs])
+            ):
+                # g[(r, c)] = 'o'
+                result += r * c
+    print(result)
+    # g.print()
+
+    # Merge F commands into counts
+    path = find_path(g)
+    path = list(path)
+    new_path = []
+    i = 0
+    while i < len(path):
+        if path[i] == "R":
+            new_path.append("R")
+            i += 1
+        elif path[i] == "L":
+            new_path.append("L")
+            i += 1
+        elif path[i] == "F":
+            count = 0
+            while i < len(path) and path[i] == "F":
+                count += 1
+                i += 1
+            new_path.append(str(count))
+        else:
+            assert False
+    path = new_path
+    print("Manually translate into commands:", "".join(path))
+
+    # manually created from above output
+    inst = (
+        "A,A,B,C,B,C,B,C,A,C\n"
+        "R,6,L,8,R,8\n"
+        "R,4,R,6,R,6,R,4,R,4\n"
+        "L,8,R,6,L,10,L,10\n"
+        "n\n"
+    )
+
+    xs = str_to_ints(data)
+    xs[0] = 2
+    a = Amp(xs)
+    for c in inst:
+        a.feed(ord(c))
+    while not a.done:
+        a.go()
+    print(a.outputs[-1])
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d18.py

@@ -0,0 +1,199 @@
+from lib import get_data, Grid2D, LETTERS_UPPER, LETTERS_LOWER, add2
+from collections import defaultdict
+
+LETTERS = LETTERS_UPPER + LETTERS_LOWER
+
+data = """#############
+#g#f.D#..h#l#
+#F###e#E###.#
+#dCba...BcIJ#
+#####.@.#####
+#nK.L...G...#
+#M###N#H###.#
+#o#m..#i#jk.#
+#############"""
+
+
+def part_1(data):
+    g = Grid2D(data)
+    (start,) = g.find("@")
+    starts = [start]
+
+    graph = defaultdict(set)
+    starts_seen = set()
+
+    while starts:
+        start = starts.pop()
+        if start in starts_seen:
+            continue
+        else:
+            starts_seen.add(start)
+
+        start_symbol = g[start]
+        xs = [start]
+        seen = set()
+
+        for steps in range(1_000):
+            nxs = []
+
+            for x in xs:
+                if x in seen:
+                    continue
+                else:
+                    seen.add(x)
+
+                for nb in g.neighbors_ort(x):
+                    if g[nb] == ".":
+                        nxs.append(nb)
+                    elif g[nb] in LETTERS:
+                        symbol = g[nb]
+                        if symbol != start_symbol:
+                            graph[symbol].add((start_symbol, steps + 1))
+                            graph[start_symbol].add((symbol, steps + 1))
+                        starts.append(nb)
+            xs = nxs
+            if len(xs) == 0:
+                break
+
+    all_keys = [g[p] for p in g.find(LETTERS_LOWER)]
+    poss = [(0, 0, tuple("@"), "@")]
+    best: dict[tuple[tuple, str], int] = {(("@",), "@"): 0}
+
+    min_dist = 10**9
+    while poss:
+        current_distance, key_count, keys, symbol = poss.pop()
+        # print(current_distance, key_count, keys, symbol)
+
+        if key_count - 1 == len(all_keys):
+            min_dist = min(min_dist, current_distance)
+            continue
+
+        for next_symbol, distance in graph[symbol]:
+            if next_symbol in LETTERS_UPPER and not next_symbol.lower() in keys:
+                continue
+
+            if next_symbol in LETTERS_LOWER:
+                new_keys = set(keys)
+                new_keys.add(next_symbol)
+                new_keys = tuple(sorted(new_keys))
+                new_key_count = len(new_keys)
+            else:
+                new_keys = keys
+                new_key_count = key_count
+
+            new_distance = current_distance + distance
+            key = (new_keys, next_symbol)
+            if (key not in best) or (key in best and best[key] > new_distance):
+                best[key] = new_distance
+                poss.append((new_distance, new_key_count, new_keys, next_symbol))
+    print(min_dist)
+
+
+def part_2(data):
+    g = Grid2D(data)
+    (start,) = g.find("@")
+    g[start] = "#"
+    g[add2(start, (-1, 0))] = "#"
+    g[add2(start, (1, 0))] = "#"
+    g[add2(start, (0, 1))] = "#"
+    g[add2(start, (0, -1))] = "#"
+
+    g[add2(start, (-1, -1))] = "0"
+    g[add2(start, (-1, 1))] = "1"
+    g[add2(start, (1, 1))] = "2"
+    g[add2(start, (1, -1))] = "3"
+
+    starts = g.find("0") + g.find("1") + g.find("2") + g.find("3")
+    graph = defaultdict(set)
+    starts_seen = set()
+
+    while starts:
+        start = starts.pop()
+        if start in starts_seen:
+            continue
+        else:
+            starts_seen.add(start)
+
+        start_symbol = g[start]
+        xs = [start]
+        seen = set()
+
+        for steps in range(1_000):
+            nxs = []
+
+            for x in xs:
+                if x in seen:
+                    continue
+                else:
+                    seen.add(x)
+
+                for nb in g.neighbors_ort(x):
+                    if g[nb] == ".":
+                        nxs.append(nb)
+                    elif g[nb] in LETTERS:
+                        symbol = g[nb]
+                        if symbol != start_symbol:
+                            graph[start].add((nb, steps + 1))
+                            graph[nb].add((start, steps + 1))
+                        starts.append(nb)
+            xs = nxs
+            if len(xs) == 0:
+                break
+    # g.print()
+
+    all_keys = [g[p] for p in g.find(LETTERS_LOWER)]
+
+    robots = tuple(g.find("0") + g.find("1") + g.find("2") + g.find("3"))
+    poss = [(0, tuple(), robots)]
+    best: dict[tuple[tuple, tuple], int] = {(tuple(), tuple()): 0}
+
+    min_dist = 10**9
+    while poss:
+        current_distance, keys, robots = poss.pop()
+
+        if len(keys) == len(all_keys):
+            min_dist = min(min_dist, current_distance)
+            # print(min_dist)
+            continue
+
+        # print(current_distance, keys, robots)
+        for robot_i in range(len(robots)):
+            robot = robots[robot_i]
+            # robot_symbol = g[robot]
+            for next_pos, distance in graph[robot]:
+                next_symbol = g[next_pos]
+
+                if next_symbol in LETTERS_UPPER and not next_symbol.lower() in keys:
+                    continue
+
+                if next_symbol in LETTERS_LOWER:
+                    new_keys = set(keys)
+                    new_keys.add(next_symbol)
+                    new_keys = tuple(sorted(new_keys))
+                else:
+                    new_keys = keys
+
+                new_distance = current_distance + distance
+
+                new_robots = list(robots)
+                new_robots[robot_i] = next_pos
+                new_robots = tuple(new_robots)
+
+                key = (new_keys, new_robots)
+                if (key not in best) or (key in best and best[key] > new_distance):
+                    best[key] = new_distance
+                    poss.append((new_distance, new_keys, new_robots))
+
+        poss = sorted(poss, key=lambda xs: (xs[0], -len(xs[1])), reverse=True)
+        poss = poss[-10000:]
+    print(min_dist)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d19.py

@@ -0,0 +1,52 @@
+from lib import get_data, str_to_ints
+from d9 import Amp
+
+
+def isin(xs, x, y):
+    a = Amp(xs, 100)
+    a.feed(x)
+    a.feed(y)
+    a.go()
+    return a.pop()
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    r = 0
+    for y in range(50):
+        for x in range(50):
+            o = isin(xs, x, y)
+            if o == 1:
+                print("#", end="")
+            else:
+                print(" ", end="")
+            r += o
+        print()
+    print(r)
+
+
+def part_2(data):
+    xs = str_to_ints(data)
+    off = 99
+    x, y = 3, 4
+    while True:
+        y += 1
+        while True:
+            o = isin(xs, x, y)
+            if o == 1:
+                break
+            x += 1
+
+        if isin(xs, x, y - off) and isin(xs, x + off, y - off) and isin(xs, x + off, y):
+            print(x * 10_000 + y - off)
+            break
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d2.py

@@ -0,0 +1,41 @@
+from lib import get_data, str_to_ints
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    xs[1] = 12
+    xs[2] = 2
+    for i in range(0, len(xs), 4):
+        match xs[i]:
+            case 1:
+                xs[xs[i + 3]] = xs[xs[i + 1]] + xs[xs[i + 2]]
+            case 2:
+                xs[xs[i + 3]] = xs[xs[i + 1]] * xs[xs[i + 2]]
+    print(xs[0])
+
+
+def part_2(data):
+    for noun in range(1, 101):
+        for verb in range(1, 101):
+            xs = str_to_ints(data)
+            xs[1] = noun
+            xs[2] = verb
+            for i in range(0, len(xs), 4):
+                match xs[i]:
+                    case 1:
+                        xs[xs[i + 3]] = xs[xs[i + 1]] + xs[xs[i + 2]]
+                    case 2:
+                        xs[xs[i + 3]] = xs[xs[i + 1]] * xs[xs[i + 2]]
+            if xs[0] == 19690720:
+                print(100 * noun + verb)
+                return
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d20.py

@@ -0,0 +1,154 @@
+from lib import get_data, Grid2D, LETTERS_UPPER
+from collections import defaultdict
+
+data = get_data(__file__)
+
+g = Grid2D(data)
+
+start = None
+end = None
+warps = defaultdict(list)
+
+inner = set()
+outer = set()
+
+for row in range(g.n_rows - 2):
+    for col in range(g.n_cols - 2):
+        a, b, c = g[(row, col)], g[(row, col + 1)], g[(row, col + 2)]
+        x, y, z = g[(row, col)], g[(row + 1, col)], g[(row + 2, col)]
+        if a in LETTERS_UPPER and b in LETTERS_UPPER and c == ".":
+            warps[a + b].append((row, col + 2))
+            if col == 0:
+                outer.add((row, col + 2))
+            else:
+                inner.add((row, col + 2))
+        elif a == "." and b in LETTERS_UPPER and c in LETTERS_UPPER:
+            warps[b + c].append((row, col))
+            if col + 3 == g.n_cols:
+                outer.add((row, col))
+            else:
+                inner.add((row, col))
+
+        if x in LETTERS_UPPER and y in LETTERS_UPPER and z == ".":
+            if x + y == "AA":
+                start = (row + 2, col)
+            else:
+                warps[x + y].append((row + 2, col))
+                if row == 0:
+                    outer.add((row + 2, col))
+                else:
+                    inner.add((row + 2, col))
+        elif x == "." and y in LETTERS_UPPER and z in LETTERS_UPPER:
+            if y + z == "ZZ":
+                end = (row, col)
+            else:
+                warps[y + z].append((row, col))
+                if row + 3 == g.n_rows:
+                    outer.add((row, col))
+                else:
+                    inner.add((row, col))
+
+
+graph = defaultdict(list)
+allnodes = set([start, end])
+for key, (a, b) in warps.items():
+    graph[a].append((b, 1))
+    graph[b].append((a, 1))
+    allnodes.add(a)
+    allnodes.add(b)
+
+for startnode in allnodes:
+    to_visit = [startnode]
+    steps = 0
+    seen = set()
+    while to_visit:
+        steps += 1
+        new_to_visit = []
+        for node in to_visit:
+            if node in seen:
+                continue
+            else:
+                seen.add(node)
+
+            assert node is not None
+            for nb in g.neighbors_ort(node):
+                if nb in seen:
+                    continue
+
+                if nb in allnodes:
+                    if not (nb, steps) in graph[startnode]:
+                        graph[startnode].append((nb, steps))
+                    if not (startnode, steps) in graph[nb]:
+                        graph[nb].append((startnode, steps))
+                    seen.add(nb)
+                elif g[nb] == ".":
+                    new_to_visit.append(nb)
+        to_visit = new_to_visit
+
+shortest = {start: 0}
+to_visit = [start]
+seen = set()
+
+while to_visit:
+    to_visit.sort(key=lambda node: shortest[node], reverse=True)
+    current = to_visit.pop()
+    if current in seen:
+        continue
+    else:
+        seen.add(current)
+
+    for nb, dist in graph[current]:
+        new_dist = shortest[current] + dist
+        if not nb in shortest:
+            shortest[nb] = new_dist
+        elif new_dist < shortest[nb]:
+            shortest[nb] = new_dist
+        if nb not in seen:
+            to_visit.append(nb)
+
+print(shortest[end])
+
+shortest = {(start, 0): 0}
+to_visit = [(start, 0)]
+seen = set()
+
+while to_visit:
+    to_visit.sort(key=lambda node: shortest[node], reverse=True)
+    current, level = to_visit.pop()
+
+    if (current, level) in seen:
+        continue
+    else:
+        seen.add((current, level))
+
+    for nb, dist in graph[current]:
+        new_dist = shortest[(current, level)] + dist
+
+        if nb == end and level == 0:
+            print(new_dist)
+            to_visit = None
+            break
+        elif nb == end:
+            continue
+        elif nb == start:
+            continue
+
+        if dist == 1:
+            if current in inner:
+                new_level = level + 1
+            elif current in outer:
+                new_level = level - 1
+            else:
+                assert False
+        else:
+            new_level = level
+
+        if new_level < 0:
+            continue
+
+        nn = (nb, new_level)
+        if not nn in shortest:
+            shortest[nn] = new_dist
+        elif new_dist < shortest[nn]:
+            shortest[nn] = new_dist
+        to_visit.append(nn)

2019/d21.py

@@ -0,0 +1,57 @@
+from lib import get_data, str_to_ints
+from d9 import Amp
+
+data = get_data(__file__)
+xs = str_to_ints(data)
+
+script = """NOT A J
+AND A J
+NOT C T
+AND D T
+OR T J
+NOT A T
+OR T J
+"""
+
+a = Amp(xs)
+while not a.done:
+    a.go()
+    if a.input_required:
+        for c in script:
+            a.feed(ord(c))
+        for c in "WALK\n":
+            a.feed(ord(c))
+
+    while a.outputs:
+        c = a.pop()
+        try:
+            chr(c)
+            # print(chr(c), end="")
+        except ValueError:
+            print(c)
+
+script = """NOT C J
+AND H J
+NOT A T
+OR T J
+NOT B T
+OR T J
+AND D J
+"""
+
+a = Amp(xs)
+while not a.done:
+    a.go()
+    if a.input_required:
+        for c in script:
+            a.feed(ord(c))
+        for c in "RUN\n":
+            a.feed(ord(c))
+
+    while a.outputs:
+        c = a.pop()
+        try:
+            chr(c)
+            # print(chr(c), end="")
+        except ValueError:
+            print(c)

2019/d22.py

@@ -0,0 +1,118 @@
+from lib import get_data, str_to_ints, mod_inverse
+from math import gcd
+
+data = get_data(__file__)
+deck = list(range(10007))
+
+# part 1
+for line in data.splitlines():
+    if "new stack" in line:
+        deck = list(reversed(deck))
+    elif "cut" in line:
+        (n,) = str_to_ints(line)
+        deck = deck[n:] + deck[:n]
+    elif "increment" in line:
+        new_deck = [-1] * len(deck)
+        pos = 0
+        (n,) = str_to_ints(line)
+        deck = list(reversed(deck))
+        while deck:
+            new_deck[pos] = deck.pop()
+            pos = (pos + n) % len(new_deck)
+        deck = new_deck
+    else:
+        assert False
+
+print(deck.index(2019))
+
+len = 10007
+orig_index = 2019
+
+# figure out how to reverse...
+index = orig_index
+for line in data.splitlines():
+    if "new stack" in line:
+        new_index = len - (index + 1)
+        rev_index = -(new_index - len + 1)
+        assert rev_index == index
+        index = new_index
+    elif "cut" in line:
+        (cut,) = str_to_ints(line)
+        cut = (len + cut) % len
+        if index >= cut:
+            new_index = index - cut
+        else:
+            new_index = (len - cut) + index
+        rev_index = (new_index + cut) % len
+        assert rev_index == index
+        index = new_index
+        # calculate index from new_index and store in rev_index
+    elif "increment" in line:
+        (n,) = str_to_ints(line)
+        assert gcd(n, len) == 1
+        new_index = (n * index) % len
+        m = mod_inverse(n, len)
+        rev_index = (new_index * m) % len
+        assert rev_index == index
+        index = new_index
+
+assert index == deck.index(2019)
+
+# check that reverse approach works
+for line in reversed(data.splitlines()):
+    if "new stack" in line:
+        index = -(index - len + 1)
+    elif "cut" in line:
+        (cut,) = str_to_ints(line)
+        cut = (len + cut) % len
+        index = (index + cut) % len
+    elif "increment" in line:
+        (n,) = str_to_ints(line)
+        assert gcd(n, len) == 1
+        m = mod_inverse(n, len)
+        index = (index * m) % len
+assert index == orig_index
+
+lines = list(reversed(data.splitlines()))
+
+# new length of deck
+len = 119315717514047
+
+# get expression for one loop using sympy
+from sympy import symbols, simplify
+
+index = symbols("index")
+expr = index
+for line in lines:
+    if "new stack" in line:
+        # index = -(index - len + 1)
+        expr = -(expr - len + 1)
+    elif "cut" in line:
+        (cut,) = str_to_ints(line)
+        cut = (len + cut) % len
+        # index = (index + cut) % len
+        expr = expr + cut
+    elif "increment" in line:
+        (n,) = str_to_ints(line)
+        assert gcd(n, len) == 1
+        m = mod_inverse(n, len)
+        # index = (index * m) % len
+        expr = expr * m
+
+# we can see that expression is in the form (a - b * i) % m
+expr = simplify(expr % len)
+coeff_dict = expr.args[0].as_coefficients_dict()
+a = coeff_dict[1]
+b = -coeff_dict[index]
+
+# math
+n_shuffles = 101741582076661
+r0 = 2020
+m = len
+p = (-b) % m
+p_t = pow(p, n_shuffles, m)
+inv_b1 = mod_inverse(b + 1, m)
+term1 = (p_t * r0) % m
+term2 = (a * (1 - p_t) * inv_b1) % m
+r_t = (term1 + term2) % m
+print(r_t)

2019/d23.py

@@ -0,0 +1,47 @@
+from lib import get_data, str_to_ints
+from d9 import Amp
+
+xs = str_to_ints(get_data(__file__))
+first_255 = True
+nat = None
+y_prev = None
+
+amps = []
+for i in range(50):
+    a = Amp(xs)
+    a.feed(i)
+    a.go()
+    amps.append(a)
+
+for j in range(1_000_000):
+    was_active = False
+    for i, a in enumerate(amps):
+        a.go()
+        if a.input_required:
+            a.feed(-1)
+
+        if len(a.outputs) > 0:
+            was_active = True
+            while len(a.outputs) < 3:
+                a.go()
+            addr = a.pop()
+            x = a.pop()
+            y = a.pop()
+            if addr == 255:
+                nat = (x, y)
+                if first_255:
+                    print(y)
+                    first_255 = False
+            else:
+                amps[addr].feed(x)
+                amps[addr].feed(y)
+
+    if not was_active and nat is not None:
+        x, y = nat
+        if y == y_prev:
+            print(y)
+            exit()
+        amps[0].feed(x)
+        amps[0].feed(y)
+        nat = None
+        y_prev = y

2019/d24.py

@@ -0,0 +1,107 @@
+from lib import get_data, Grid2D, add2
+from collections import defaultdict
+
+
+data = get_data(__file__)
+
+g = Grid2D(data)
+seen = set()
+while True:
+    h = g.hash()
+    if h in seen:
+        break
+    else:
+        seen.add(h)
+
+    gn = g.clone_with_val(".")
+    for r in range(g.n_rows):
+        for c in range(g.n_cols):
+            p = (r, c)
+            nb_bugs = sum(1 for nb in g.neighbors_ort(p) if g[nb] == "#")
+            if g[p] == "#" and nb_bugs == 1:
+                gn[p] = "#"
+            if g[p] == "." and nb_bugs in [1, 2]:
+                gn[p] = "#"
+    g = gn
+
+
+t = 0
+p = 1
+for r in range(g.n_rows):
+    for c in range(g.n_cols):
+        if g[(r, c)] == "#":
+            t += p
+        p *= 2
+print(t)
+
+N = (-1, 0)
+E = (0, 1)
+S = (1, 0)
+W = (0, -1)
+DIRS = [N, E, S, W]
+ROW, COL = 0, 1
+
+# data = get_data(__file__)
+g = Grid2D(data)
+bugs = [(0, r, c) for (r, c) in g.find("#")]
+middle = (g.n_rows // 2, g.n_cols // 2)
+rows, cols = g.n_rows, g.n_cols
+
+
+def get_edge(side):
+    edges = {
+        S: [(0, c) for c in range(cols)],
+        N: [(rows - 1, c) for c in range(cols)],
+        W: [(r, cols - 1) for r in range(rows)],
+        E: [(r, 0) for r in range(rows)],
+    }
+    return edges[side]
+
+
+def get_neighbors(pos):
+    level, row, col = pos
+    neighbors = []
+
+    for d in DIRS:
+        nb = add2((row, col), d)
+        if nb == middle:
+            for ir, ic in get_edge(d):
+                neighbors.append((level - 1, ir, ic))
+        elif nb[ROW] in {-1, rows} or nb[COL] in {-1, cols}:
+            nr, nc = nb
+            if nr == -1:
+                neighbors.append((level + 1, *add2(middle, N)))
+            if nr == rows:
+                neighbors.append((level + 1, *add2(middle, S)))
+            if nc == -1:
+                neighbors.append((level + 1, *add2(middle, W)))
+            if nc == cols:
+                neighbors.append((level + 1, *add2(middle, E)))
+        else:
+            nr, nc = nb
+            neighbors.append((level, nr, nc))
+    return neighbors
+
+
+assert len(get_neighbors((0, 1, 1))) == 4
+assert len(get_neighbors((0, 3, 3))) == 4
+assert len(get_neighbors((0, 0, 3))) == 4
+assert len(get_neighbors((0, 0, 4))) == 4
+assert len(get_neighbors((0, 2, 3))) == 8
+
+for _ in range(200):
+    neighbors = defaultdict(int)
+    current_bugs = set(bugs)
+    for pos in bugs:
+        for nb in get_neighbors(pos):
+            neighbors[nb] += 1
+
+    new_bugs = []
+    for pos, count in neighbors.items():
+        if pos in current_bugs and count == 1:
+            new_bugs.append(pos)
+        if pos not in current_bugs and count in [1, 2]:
+            new_bugs.append(pos)
+    bugs = new_bugs
+
+print(len(bugs))

2019/d25.py

@@ -0,0 +1,160 @@
+from lib import get_data, ints
+from d9 import Amp
+from itertools import combinations
+
+data = get_data(__file__)
+xs = ints(data)
+
+commands = [
+    "north",
+    "take candy cane",
+    "west",
+    "south",
+    "south",
+    "take fuel cell",
+    "south",
+    "take manifold",
+    "north",
+    "north",
+    "west",
+    "take mutex",
+    "north",
+    "south",
+    "south",
+    "south",
+    "take coin",
+    "south",
+    "north",
+    "east",
+    "take cake",
+    "west",
+    "east",
+    "north",
+    "south",
+    "west",
+    "east",
+    "east",
+    "north",
+    "south",
+    "west",
+    "north",
+    "west",
+    "east",
+    "west",
+    "south",
+    "west",
+    "north",
+    "north",
+    "south",
+    "west",
+    "north",
+    "east",
+    "south",
+    "west",
+    "east",
+    "west",
+    "south",
+    "west",
+    "take dehydrated water",
+    "west",
+    "east",
+    "west",
+    "south",
+    "take prime number",
+    "south",
+    "north",
+    "east",
+    "east",
+    "west",
+    "north",
+    "east",
+    "east",
+    "north",
+    "south",
+    "west",
+    "north",
+    "west",
+    "south",
+    "inv",
+    "west",
+]
+
+items = [
+    "cake",
+    "prime number",
+    "mutex",
+    "dehydrated water",
+    "coin",
+    "manifold",
+    "candy cane",
+    "fuel cell",
+]
+
+
+def run_command(a, s):
+    for c in s:
+        a.feed(ord(c))
+    a.feed(10)
+    a.go()
+
+
+a = Amp(xs)
+for c in commands:
+    a.go()
+    while a.outputs:
+        a.go()
+        a.pop()
+        # print(chr(a.pop()), end="")
+    run_command(a, c)
+    a.go()
+
+
+def try_all(a):
+    subsets = [list(combinations(items, r)) for r in range(1, len(items) + 1)]
+    subsets = [item for sublist in subsets for item in sublist]
+    for subset in subsets:
+        for item in items:
+            c = f"drop {item}"
+            run_command(a, c)
+            a.go()
+            while a.outputs:
+                a.pop()
+                a.go()
+
+        for item in subset:
+            c = f"take {item}"
+            run_command(a, c)
+            a.go()
+            while a.outputs:
+                a.pop()
+                a.go()
+
+        run_command(a, "west")
+
+        output_str = ""
+        while a.outputs:
+            a.go()
+            output_str += chr(a.pop())
+        if "lighter" in output_str:
+            pass
+        elif "heavier" in output_str:
+            pass
+        else:
+            (password,) = ints(output_str)
+            print(password)
+            exit()
+
+
+while True:
+    a.go()
+
+    output_str = ""
+    while a.outputs:
+        a.go()
+        output_str += chr(a.pop())
+
+    try_all(a)
+
+    if a.input_required:
+        c = input(">")
+        run_command(a, c)

2019/d3.py

@@ -0,0 +1,57 @@
+from lib import get_data, add2
+
+
+DIRS = {"R": (0, 1), "U": (-1, 0), "D": (1, 0), "L": (0, -1)}
+
+
+def part_1(data):
+    xss = []
+    for path in data.splitlines():
+        xs = [(0, 0)]
+        for word in path.split(","):
+            dir = DIRS[word[0]]
+            x = int(word[1:])
+            for _ in range(x):
+                xs.append(add2(xs[-1], dir))
+        xss.append(xs)
+    ys = set(xss[0]) & set(xss[1])
+    ys.remove((0, 0))
+    min_dist = 10**9
+    for y in ys:
+        d = abs(y[0]) + abs(y[1])
+        min_dist = min(min_dist, d)
+    print(min_dist)
+
+
+def part_2(data):
+    xss = []
+    for path in data.splitlines():
+        pos = (0, 0)
+        steps = 0
+        xs = {}
+        for word in path.split(","):
+            dir = DIRS[word[0]]
+            x = int(word[1:])
+            for _ in range(x):
+                steps += 1
+                pos = add2(pos, dir)
+                if not pos in xs:
+                    xs[pos] = steps
+        xss.append(xs)
+
+    min_steps = 10**9
+    for x in xss[0].keys():
+        if x in xss[1]:
+            steps = xss[0][x] + xss[1][x]
+            min_steps = min(steps, min_steps)
+    print(min_steps)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d4.py

@@ -0,0 +1,70 @@
+from lib import get_data, str_to_ints
+
+
+def in_range_1(x):
+    contains_double = False
+    s = str(x)
+    for i in range(len(s) - 1):
+        if s[i] == s[i + 1]:
+            contains_double = True
+            break
+
+    if not contains_double:
+        return False
+
+    for i in range(len(s) - 1):
+        if ord(s[i]) > ord(s[i + 1]):
+            return False
+    return True
+
+
+def in_range_2(x):
+    contains_double = False
+    s = str(x)
+    for i in range(len(s) - 1):
+        if s[i] == s[i + 1]:
+            if i + 2 < len(s):
+                if s[i + 2] == s[i + 1]:
+                    continue
+            if i - 1 >= 0:
+                if s[i - 1] == s[i]:
+                    continue
+            contains_double = True
+
+    if not contains_double:
+        return False
+
+    for i in range(len(s) - 1):
+        if ord(s[i]) > ord(s[i + 1]):
+            return False
+    return True
+
+
+def part_1(data):
+    a, b = str_to_ints(data)
+    b = -b
+    r = 0
+    for x in range(a, b + 1):
+        if in_range_1(x):
+            r += 1
+    print(r)
+
+
+def part_2(data):
+    a, b = str_to_ints(data)
+    b = -b
+    r = 0
+    for x in range(a, b + 1):
+        if in_range_2(x):
+            r += 1
+    print(r)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d5.py

@@ -0,0 +1,123 @@
+from lib import get_data, str_to_ints
+
+
+def part_1(data):
+    xs = str_to_ints(data)
+    i = 0
+    while i < len(xs):
+        inst = str(xs[i])
+        inst = "0" * (5 - len(inst)) + inst
+        assert len(inst) == 5
+        op = int(inst[3:5])
+        mode_p1 = int(inst[2])
+        mode_p2 = int(inst[1])
+        mode_p3 = int(inst[0])
+        match op:
+            case 1:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                assert mode_p3 == 0
+                xs[xs[i + 3]] = p1 + p2
+                i += 4
+            case 2:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                assert mode_p3 == 0
+                xs[xs[i + 3]] = p1 * p2
+                i += 4
+            case 3:
+                print("input", i, 1)
+                assert mode_p1 == 0
+                xs[xs[i + 1]] = 1
+                i += 2
+            case 4:
+                if mode_p1 == 0:
+                    v = xs[xs[i + 1]]
+                else:
+                    v = xs[i + 1]
+                print("output", v)
+                i += 2
+            case 99:
+                break
+
+
+def part_2(data):
+    xs = str_to_ints(data)
+    i = 0
+    while i < len(xs):
+        inst = str(xs[i])
+        inst = "0" * (5 - len(inst)) + inst
+        assert len(inst) == 5
+        op = int(inst[3:5])
+        mode_p1 = int(inst[2])
+        mode_p2 = int(inst[1])
+        mode_p3 = int(inst[0])
+        match op:
+            case 1:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                assert mode_p3 == 0
+                xs[xs[i + 3]] = p1 + p2
+                i += 4
+            case 2:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                assert mode_p3 == 0
+                xs[xs[i + 3]] = p1 * p2
+                i += 4
+            case 3:
+                print("input", i, 5)
+                assert mode_p1 == 0
+                xs[xs[i + 1]] = 5
+                i += 2
+            case 4:
+                if mode_p1 == 0:
+                    v = xs[xs[i + 1]]
+                else:
+                    v = xs[i + 1]
+                print("output", v)
+                i += 2
+            case 99:
+                break
+            case 5:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                if p1 != 0:
+                    i = p2
+                else:
+                    i += 3
+            case 6:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                if p1 == 0:
+                    i = p2
+                else:
+                    i += 3
+            case 7:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                assert mode_p3 == 0
+                if p1 < p2:
+                    xs[xs[i + 3]] = 1
+                else:
+                    xs[xs[i + 3]] = 0
+                i += 4
+            case 8:
+                p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                assert mode_p3 == 0
+                if p1 == p2:
+                    xs[xs[i + 3]] = 1
+                else:
+                    xs[xs[i + 3]] = 0
+                i += 4
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d6.py

@@ -0,0 +1,57 @@
+from lib import get_data, str_to_ints
+from collections import defaultdict
+
+
+def part_1(data):
+    orbits = defaultdict(list)
+    for line in data.splitlines():
+        a, b = line.split(")")
+        orbits[a].append(b)
+
+    count = 0
+    for key in orbits.keys():
+        seen = set()
+        around = list(orbits[key])
+        while around:
+            a = around.pop()
+            count += 1
+            if a in orbits:
+                for o in orbits[a]:
+                    if o not in seen:
+                        around.append(o)
+            seen.add(a)
+    print(count)
+
+
+def part_2(data):
+    g = defaultdict(list)
+    for line in data.splitlines():
+        a, b = line.split(")")
+        g[a].append(b)
+        g[b].append(a)
+
+    seen = set()
+    nodes = ["YOU"]
+    steps = 0
+    while True:
+        new_nodes = []
+        for node in nodes:
+            seen.add(node)
+            for nb in g[node]:
+                if nb not in seen:
+                    new_nodes.append(nb)
+                if nb == "SAN":
+                    print(steps - 1)
+                    return
+        nodes = new_nodes
+        steps += 1
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d7.py

@@ -0,0 +1,144 @@
+from lib import get_data, str_to_ints
+from itertools import permutations
+
+
+class Amp:
+    def __init__(self, xs):
+        self.xs = list(xs)
+        self.i = 0
+        self.inputs = []
+        self.outputs = []
+        self.done = False
+
+    def feed(self, input):
+        self.inputs.append(input)
+
+    def pop(self):
+        v = self.outputs[0]
+        self.outputs = self.outputs[1:]
+        return v
+
+    def go(self):
+        xs = self.xs
+        i = self.i
+        while i < len(xs):
+            inst = str(xs[i])
+            inst = "0" * (5 - len(inst)) + inst
+            assert len(inst) == 5
+            op = int(inst[3:5])
+            mode_p1 = int(inst[2])
+            mode_p2 = int(inst[1])
+            mode_p3 = int(inst[0])
+            match op:
+                case 1:
+                    p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                    p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                    assert mode_p3 == 0
+                    xs[xs[i + 3]] = p1 + p2
+                    i += 4
+                case 2:
+                    p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                    p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                    assert mode_p3 == 0
+                    xs[xs[i + 3]] = p1 * p2
+                    i += 4
+                case 3:
+                    assert mode_p1 == 0
+                    assert len(self.inputs) > 0
+                    xs[xs[i + 1]] = self.inputs[0]
+                    self.inputs = self.inputs[1:]
+                    i += 2
+                case 4:
+                    if mode_p1 == 0:
+                        v = xs[xs[i + 1]]
+                    else:
+                        v = xs[i + 1]
+                    self.outputs.append(v)
+                    i += 2
+                    self.i = i
+                    return
+                case 99:
+                    self.done = True
+                    return
+                case 5:
+                    p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                    p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                    if p1 != 0:
+                        i = p2
+                    else:
+                        i += 3
+                case 6:
+                    p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                    p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                    if p1 == 0:
+                        i = p2
+                    else:
+                        i += 3
+                case 7:
+                    p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                    p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                    assert mode_p3 == 0
+                    if p1 < p2:
+                        xs[xs[i + 3]] = 1
+                    else:
+                        xs[xs[i + 3]] = 0
+                    i += 4
+                case 8:
+                    p1 = xs[xs[i + 1]] if mode_p1 == 0 else xs[i + 1]
+                    p2 = xs[xs[i + 2]] if mode_p2 == 0 else xs[i + 2]
+                    assert mode_p3 == 0
+                    if p1 == p2:
+                        xs[xs[i + 3]] = 1
+                    else:
+                        xs[xs[i + 3]] = 0
+                    i += 4
+            self.i = i
+
+
+def part_1(data):
+    xs_orig = str_to_ints(data)
+    max_output = 0
+    for ps in permutations(list(range(5))):
+        current_output = 0
+        for p in ps:
+            a = Amp(xs_orig)
+            a.feed(p)
+            a.feed(current_output)
+            a.go()
+            assert len(a.outputs) == 1
+            current_output = a.outputs.pop()
+        max_output = max(max_output, current_output)
+    print(max_output)
+
+
+def part_2(data):
+    xs_orig = str_to_ints(data)
+    max_output = 0
+    for ps in permutations(list(range(5, 10))):
+        amps = [Amp(xs_orig) for _ in range(len(ps))]
+        for i, p in enumerate(ps):
+            amps[i].feed(p)
+
+        current_output = 0
+        current_amp_i = 0
+        while True:
+            amps[current_amp_i].feed(current_output)
+            amps[current_amp_i].go()
+            if amps[current_amp_i].done:
+                max_output = max(max_output, current_output)
+                break
+            assert len(amps[current_amp_i].outputs) == 1
+            current_output = amps[current_amp_i].outputs.pop()
+            current_amp_i = (current_amp_i + 1) % len(amps)
+
+    print(max_output)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d8.py

@@ -0,0 +1,70 @@
+from lib import get_data
+
+
+def part_1(data):
+    wide = 25
+    tall = 6
+    xs = [int(c) for c in data.strip()]
+    layers = []
+    i = 0
+    while i < len(xs):
+        if i % (wide * tall) == 0:
+            layers.append([])
+        layers[-1].append(xs[i])
+        i += 1
+
+    min_zero_layer = None
+    min_zeros = 10**9
+    for layer in layers:
+        zeros = layer.count(0)
+        if zeros < min_zeros:
+            min_zeros = zeros
+            min_zero_layer = layer
+    assert min_zero_layer is not None
+    ones = min_zero_layer.count(1)
+    twos = min_zero_layer.count(2)
+    print(ones * twos)
+
+
+def part_2(data):
+    wide = 25
+    tall = 6
+    xs = [int(c) for c in data.strip()]
+    layers = []
+    i = 0
+    while i < len(xs):
+        if i % (wide * tall) == 0:
+            layers.append([])
+        layers[-1].append(xs[i])
+        i += 1
+    result = []
+    for i in range(wide * tall):
+        current = 2
+        for layer in layers:
+            pixel = layer[i]
+            if current == 2:
+                current = pixel
+        result.append(current)
+
+    for row in range(tall):
+        row_str = ""
+        for col in range(wide):
+            pixel_idx = row * wide + col
+            pixel = result[pixel_idx]
+            if pixel == 0:
+                row_str += "⬛"
+            elif pixel == 1:
+                row_str += "⬜"
+            else:
+                assert False
+        print(row_str)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2019/d9.py

@@ -0,0 +1,154 @@
+from lib import get_data, str_to_ints
+
+
+class Amp:
+    def __init__(self, xs, buffer_extra=10000):
+        self.xs = list(xs)
+        self.xs += [0 for _ in range(buffer_extra)]
+        self.i = 0
+        self.inputs = []
+        self.outputs = []
+        self.done = False
+        self.input_required = False
+        self.rel_base = 0
+
+    def feed(self, input):
+        self.input_required = False
+        self.inputs.append(input)
+
+    def pop(self):
+        v = self.outputs[0]
+        self.outputs = self.outputs[1:]
+        return v
+
+    def get_param(self, offset, mode):
+        if mode == 0:
+            p = self.xs[self.xs[offset]]
+        elif mode == 1:
+            p = self.xs[offset]
+        elif mode == 2:
+            assert self.rel_base + offset >= 0
+            p = self.xs[self.rel_base + self.xs[offset]]
+        else:
+            assert False
+        return p
+
+    def get_addr(self, offset, mode):
+        if mode == 0:
+            return self.xs[offset]
+        elif mode == 2:
+            return self.rel_base + self.xs[offset]
+        else:
+            assert False
+
+    def go(self):
+        xs = self.xs
+        i = self.i
+        while i < len(xs):
+            assert xs[i] >= 0
+            inst = str(xs[i])
+            inst = "0" * (5 - len(inst)) + inst
+            assert len(inst) == 5
+            op = int(inst[3:5])
+            mode_p1 = int(inst[2])
+            mode_p2 = int(inst[1])
+            mode_p3 = int(inst[0])
+            match op:
+                case 1:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    p2 = self.get_param(i + 2, mode_p2)
+                    addr = self.get_addr(i + 3, mode_p3)
+                    xs[addr] = p1 + p2
+                    i += 4
+                case 2:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    p2 = self.get_param(i + 2, mode_p2)
+                    addr = self.get_addr(i + 3, mode_p3)
+                    xs[addr] = p1 * p2
+                    i += 4
+                case 3:
+                    # read input
+                    if len(self.inputs) == 0:
+                        self.i = i
+                        self.input_required = True
+                        return
+                    addr = self.get_addr(i + 1, mode_p1)
+                    xs[addr] = self.inputs[0]
+                    self.inputs = self.inputs[1:]
+                    i += 2
+                case 4:
+                    # output
+                    v = self.get_param(i + 1, mode_p1)
+                    self.outputs.append(v)
+                    i += 2
+                    self.i = i
+                    return
+                case 99:
+                    self.done = True
+                    return
+                case 5:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    p2 = self.get_param(i + 2, mode_p2)
+                    if p1 != 0:
+                        i = p2
+                    else:
+                        i += 3
+                case 6:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    p2 = self.get_param(i + 2, mode_p2)
+                    if p1 == 0:
+                        i = p2
+                    else:
+                        i += 3
+                case 7:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    p2 = self.get_param(i + 2, mode_p2)
+                    addr = self.get_addr(i + 3, mode_p3)
+                    if p1 < p2:
+                        xs[addr] = 1
+                    else:
+                        xs[addr] = 0
+                    i += 4
+                case 8:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    p2 = self.get_param(i + 2, mode_p2)
+                    addr = self.get_addr(i + 3, mode_p3)
+                    if p1 == p2:
+                        xs[addr] = 1
+                    else:
+                        xs[addr] = 0
+                    i += 4
+                case 9:
+                    p1 = self.get_param(i + 1, mode_p1)
+                    self.rel_base += p1
+                    i += 2
+                case _:
+                    assert False
+            self.i = i
+
+
+def part_1(data):
+    xs_orig = str_to_ints(data)
+
+    a = Amp(xs_orig)
+    a.feed(1)
+    while not a.done:
+        a.go()
+        a.go()
+        print(a.pop())
+
+    a = Amp(xs_orig)
+    a.feed(2)
+    while not a.done:
+        a.go()
+        a.go()
+        print(a.pop())
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2019/lib.py

@@ -0,0 +1 @@
+../lib.py

2019/monitor.py

@@ -0,0 +1 @@
+../monitor.py

2020/d1.py

@@ -0,0 +1,31 @@
+from lib import get_data, str_to_ints
+
+
+def part_1(data):
+    xs = sorted(str_to_ints(data))
+
+    for i in range(len(xs)):
+        for j in range(i + 1, len(xs)):
+            a, b = xs[i], xs[j]
+            if a + b == 2020:
+                print(a * b)
+            if a + b > 2020:
+                break
+
+    for i in range(len(xs)):
+        for j in range(i + 1, len(xs)):
+            for k in range(j + 1, len(xs)):
+                a, b, c = xs[i], xs[j], xs[k]
+                if a + b + c == 2020:
+                    print(a * b * c)
+                if a + b + c > 2020:
+                    break
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d10.py

@@ -0,0 +1,57 @@
+from lib import get_data
+from collections import defaultdict
+from functools import lru_cache
+
+
+@lru_cache
+def count(xs, current, target):
+    delta_target = target - current
+    if len(xs) == 0:
+        if delta_target <= 3:
+            return 1
+        else:
+            return 0
+
+    x = xs[0]
+    xs = xs[1:]
+
+    total = 0
+    delta = x - current
+
+    if delta > 3:
+        return 0
+
+    if delta <= 3:
+        total += count(xs, x, target)
+
+    total += count(xs, current, target)
+    return total
+
+
+def part_1(data):
+    xs = list(map(int, data.strip().splitlines()))
+    out = max(xs) + 3
+    ds = defaultdict(int)
+
+    c = 0
+    for x in sorted(xs):
+        d = x - c
+        ds[d] += 1
+        c = x
+    d = out - c
+    ds[d] += 1
+
+    a, b = list(ds.values())
+    print(a * b)
+
+    xs = tuple(sorted(xs))
+    print(count(xs, 0, out))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d11.py

@@ -0,0 +1,89 @@
+from lib import get_data, Grid2D, add2
+
+data = """L.LL.LL.LL
+LLLLLLL.LL
+L.L.L..L..
+LLLL.LL.LL
+L.LL.LL.LL
+L.LLLLL.LL
+..L.L.....
+LLLLLLLLLL
+L.LLLLLL.L
+L.LLLLL.LL"""
+
+
+def part_1(data):
+    g = Grid2D(data)
+    seen = set()
+    while True:
+        h = g.hash()
+        if h in seen:
+            break
+        seen.add(h)
+
+        ng = g.clone_with_val(".")
+        for r in range(g.n_rows):
+            for c in range(g.n_cols):
+                p = (r, c)
+                s = g[p]
+                if s == ".":
+                    continue
+                occupied = sum([1 if g[nb] == "#" else 0 for nb in g.neighbors_adj(p)])
+                if s == "L" and occupied == 0:
+                    ng[p] = "#"
+                elif s == "#" and occupied >= 4:
+                    ng[p] = "L"
+                else:
+                    ng[p] = s
+        g = ng
+    print(len(g.find("#")))
+
+
+def part_2(data):
+    g = Grid2D(data)
+    seen = set()
+    while True:
+        h = g.hash()
+        if h in seen:
+            break
+        seen.add(h)
+
+        ng = g.clone_with_val(".")
+        for r in range(g.n_rows):
+            for c in range(g.n_cols):
+                p = (r, c)
+                s = g[p]
+                if s == ".":
+                    continue
+
+                occupied = 0
+                for dir in g.COORDS_ORTH + g.COORDS_DIAG:
+                    np = p
+                    while True:
+                        np = add2(np, dir)
+                        if not g.contains(np):
+                            break
+                        elif g[np] == "#":
+                            occupied += 1
+                            break
+                        elif g[np] == "L":
+                            break
+
+                if s == "L" and occupied == 0:
+                    ng[p] = "#"
+                elif s == "#" and occupied >= 5:
+                    ng[p] = "L"
+                else:
+                    ng[p] = s
+        g = ng
+    print(len(g.find("#")))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d12.py

@@ -0,0 +1,82 @@
+from lib import get_data
+
+DIRS = {
+    "N": (-1, 0),
+    "E": (0, 1),
+    "S": (1, 0),
+    "W": (0, -1),
+}
+
+
+def part_1(data):
+    dir_key = "E"
+    pos = 0, 0
+    dirs = "NESW"
+
+    for line in data.splitlines():
+        c = line[0]
+        v = int(line[1:])
+        if c in DIRS.keys():
+            pos = pos[0] + v * DIRS[c][0], pos[1] + v * DIRS[c][1]
+        elif c == "F":
+            dir = DIRS[dir_key]
+            pos = (pos[0] + v * dir[0], pos[1] + v * dir[1])
+        elif c == "R":
+            assert v % 90 == 0
+            dir_key = dirs[(dirs.index(dir_key) + v // 90) % len(dirs)]
+        elif c == "L":
+            assert v % 90 == 0
+            dir_key = dirs[(dirs.index(dir_key) - v // 90) % len(dirs)]
+        else:
+            print(c, v)
+            assert False
+    print(sum(map(abs, pos)))
+
+
+def part_2(data):
+    way_point = (-1, 10)
+    pos = 0, 0
+
+    for line in data.splitlines():
+        c = line[0]
+        v = int(line[1:])
+        if c in DIRS.keys():
+            way_point = way_point[0] + v * DIRS[c][0], way_point[1] + v * DIRS[c][1]
+        elif c == "F":
+            pos = (pos[0] + v * way_point[0], pos[1] + v * way_point[1])
+        elif c == "R":
+            row, col = way_point
+            if v == 90:
+                way_point = (col, -row)
+            elif v == 180:
+                way_point = (-row, -col)
+            elif v == 270:
+                way_point = (-col, row)
+            else:
+                print(c, v)
+                assert False
+        elif c == "L":
+            row, col = way_point
+            if v == 90:
+                way_point = (-col, row)
+            elif v == 180:
+                way_point = (-row, -col)
+            elif v == 270:
+                way_point = (col, -row)
+            else:
+                print(c, v)
+                assert False
+        else:
+            print(c, v)
+            assert False
+    print(sum(map(abs, pos)))
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d13.py

@@ -0,0 +1,39 @@
+from lib import get_data, str_to_ints, mod_inverse
+from functools import reduce
+
+data = get_data(__file__)
+lines = data.splitlines()
+
+earliest = int(lines[0])
+times = str_to_ints(lines[1])
+
+mintime = 10**21
+id = None
+
+for time in times:
+    mintimecur = (earliest // time) * time + time
+    if mintimecur < mintime:
+        mintime = mintimecur
+        id = time
+
+
+assert id is not None
+print((mintime - earliest) * id)
+
+fields = lines[1].split(",")
+
+buses = []
+for offset, busid in enumerate(fields):
+    if busid == "x":
+        continue
+    period = int(busid)
+    buses.append((period, -offset % period))
+
+
+total = 0
+product = reduce(lambda a, b: a * b, map(lambda x: x[0], buses))
+for period, offset in buses:
+    p = product // period
+    total += offset * mod_inverse(p, period) * p
+
+print(total % product)

2020/d14.py

@@ -0,0 +1,77 @@
+from lib import get_data, str_to_ints
+from collections import defaultdict
+
+data = """mask = XXXXXXXXXXXXXXXXXXXXXXXXXXXXX1XXXX0X
+mem[8] = 11
+mem[7] = 101
+mem[8] = 0
+"""
+data = get_data(__file__)
+
+mem = defaultdict(int)
+mfix, mopt = None, None
+for line in data.splitlines():
+    if line.startswith("mask"):
+        fix = "0b"
+        opt = "0b"
+        for c in line[7:]:
+            if c == "1":
+                fix += "1"
+                opt += "0"
+            elif c == "0":
+                fix += "0"
+                opt += "0"
+            elif c == "X":
+                fix += "0"
+                opt += "1"
+            else:
+                assert False
+        mfix = int(fix, 2)
+        mopt = int(opt, 2)
+    elif line.startswith("mem"):
+        assert mfix is not None and mopt is not None
+        addr, value = str_to_ints(line)
+        value = mfix | (value & mopt)
+        mem[addr] = value
+
+print(sum(v for v in mem.values()))
+
+mem = defaultdict(int)
+masks = []
+for line in data.splitlines():
+    if line.startswith("mask"):
+        fix = ["0b"]
+        opt = ["0b"]
+        for c in line[7:]:
+            if c == "0":
+                fix = [f + "0" for f in fix]
+                opt = [o + "1" for o in opt]
+            elif c == "1":
+                fix = [f + "1" for f in fix]
+                opt = [o + "0" for o in opt]
+            elif c == "X":
+                nfix = []
+                nopt = []
+                for f in fix:
+                    nfix.append(f + "0")
+                    nfix.append(f + "1")
+                for o in opt:
+                    nopt.append(o + "0")
+                    nopt.append(o + "0")
+                fix = nfix
+                opt = nopt
+            else:
+                assert False
+        masks = tuple(
+            zip(
+                tuple(map(lambda f: int(f, 2), fix)),
+                tuple(map(lambda o: int(o, 2), opt)),
+            )
+        )
+    elif line.startswith("mem"):
+        addr, value = str_to_ints(line)
+        for fix, opt in masks:
+            addr_ = fix | (addr & opt)
+            mem[addr_] = value
+
+print(sum(v for v in mem.values()))

2020/d15.py

@@ -0,0 +1,22 @@
+from lib import get_data, str_to_ints
+from collections import defaultdict
+
+data = get_data(__file__)
+
+for limit in [2021, 30000001]:
+    xs = list(reversed(str_to_ints(data)))
+    spoken = defaultdict(list)
+    recent = None
+    for turn in range(1, limit):
+        if len(xs) > 0:
+            recent = xs.pop()
+            spoken[recent].append(turn)
+        else:
+            if recent in spoken and len(spoken[recent]) == 1:
+                recent = 0
+            elif recent in spoken:
+                recent = spoken[recent][-1] - spoken[recent][-2]
+            else:
+                recent = 0
+            spoken[recent].append(turn)
+    print(recent)

2020/d16.py

@@ -0,0 +1,88 @@
+from lib import get_data, str_to_ints
+
+data = get_data(__file__)
+
+dps = []
+ranges = []
+lines = (l for l in data.splitlines())
+
+index = 0
+for line in lines:
+    if line.strip() == "":
+        break
+    if line.startswith("departure"):
+        dps.append(index)
+    a, b, c, d = str_to_ints(line.replace("-", " "))
+    # ranges.append(((a, b), (c, d)))
+    ranges.append((a, b, c, d))
+    index += 1
+
+next(lines)
+my_ticket = str_to_ints(next(lines))
+next(lines)
+next(lines)
+
+error = 0
+valid = []
+fields = []
+for line in lines:
+    # print(line)
+    has_error = False
+    field = []
+    for x in str_to_ints(line):
+        no_match = True
+        field.append(set())
+        for i, (a, b, c, d) in enumerate(ranges):
+            if a <= x <= b:
+                field[-1].add(i)
+                no_match = False
+            elif c <= x <= d:
+                field[-1].add(i)
+                no_match = False
+        if no_match:
+            has_error = True
+            error += x
+    if not has_error:
+        valid.append(line)
+        fields.append(field)
+
+base = fields[0]
+for field in fields[1:]:
+    for i in range(len(field)):
+        base[i] &= field[i]
+print(error)
+
+used = set()
+done = False
+base = [list(xs) for xs in base]
+while not done:
+    done = True
+    single = None
+    for xs in base:
+        if len(xs) == 1 and xs[0] not in used:
+            single = xs[0]
+            used.add(single)
+            break
+
+    if single is not None:
+        for xs in base:
+            if len(xs) == 1:
+                continue
+            if single in xs:
+                xs.remove(single)
+
+    for xs in base:
+        if len(xs) != 1:
+            done = False
+            break
+
+mapping = []
+for xs in base:
+    (x,) = xs
+    mapping.append(x)
+
+r = 1
+for i, v in zip(mapping, my_ticket):
+    if i in dps:
+        r *= v
+print(r)

2020/d17.py

@@ -0,0 +1,42 @@
+from itertools import product
+from lib import get_data
+from collections import defaultdict
+
+data = get_data(__file__)
+
+
+def neighbors(p):
+    d = len(p)
+    for xs in product(range(-1, 2), repeat=d):
+        if all(x == 0 for x in xs):
+            continue
+        yield tuple([p[i] + xs[i] for i in range(len(xs))])
+
+
+for d in [3, 4]:
+    points = set()
+    lines = data.splitlines()
+    for y in range(len(lines)):
+        for x in range(len(lines[0])):
+            if lines[y][x] == "#":
+                points.add(tuple([x, y] + [0] * (d - 2)))
+
+    for _ in range(6):
+        new_points = set()
+        actives = defaultdict(int)
+        for p in points:
+            nbcount = 0
+            for nb in neighbors(p):
+                actives[nb] += 1
+                if nb in points:
+                    nbcount += 1
+            if nbcount == 2 or nbcount == 3:
+                new_points.add(p)
+        for p, count in actives.items():
+            if p in points:
+                continue
+            elif count == 3:
+                new_points.add(p)
+        points = new_points
+
+    print(len(points))

2020/d18.py

@@ -0,0 +1,106 @@
+from lib import get_data
+
+
+def eval_1(s) -> int:
+    if type(s) is int:
+        return s
+    i = 0
+    parts = []
+    while i < len(s):
+        if s[i] == "(":
+            nested = 1
+            r = "("
+            i += 1
+            while nested > 0:
+                r += s[i]
+                if s[i] == ")":
+                    nested -= 1
+                elif s[i] == "(":
+                    nested += 1
+                i += 1
+            parts.append(r[1:-1])
+        elif s[i].isdigit():
+            d = ""
+            while i < len(s) and s[i].isdigit():
+                d += s[i]
+                i += 1
+            parts.append(int(d))
+        elif s[i] == " ":
+            pass
+        elif s[i] == "*" or s[i] == "+":
+            parts.append(s[i])
+        i += 1
+
+    i = 0
+    while len(parts) > 1:
+        if parts[1] == "*":
+            parts[2] = eval_1(parts[0]) * eval_1(parts[2])
+            parts = parts[2:]
+        elif parts[1] == "+":
+            parts[2] = eval_1(parts[0]) + eval_1(parts[2])
+            parts = parts[2:]
+        else:
+            assert False
+    return parts[-1]
+
+
+def eval_2(s) -> int:
+    if type(s) is int:
+        return s
+    i = 0
+    parts = []
+    while i < len(s):
+        if s[i] == "(":
+            nested = 1
+            r = "("
+            i += 1
+            while nested > 0:
+                r += s[i]
+                if s[i] == ")":
+                    nested -= 1
+                elif s[i] == "(":
+                    nested += 1
+                i += 1
+            parts.append(r[1:-1])
+        elif s[i].isdigit():
+            d = ""
+            while i < len(s) and s[i].isdigit():
+                d += s[i]
+                i += 1
+            parts.append(int(d))
+        elif s[i] == " ":
+            pass
+        elif s[i] == "*" or s[i] == "+":
+            parts.append(s[i])
+        i += 1
+
+    while len(parts) > 1:
+        new_parts = []
+        for i in range(0, len(parts) - 1, 2):
+            if parts[i + 1] == "+":
+                new_parts.append(eval_2(parts[i]) + eval_2(parts[i + 2]))
+                new_parts += parts[i + 3 :]
+                break
+            elif parts[1] == "*":
+                new_parts.append(parts[i])
+                new_parts.append(parts[i + 1])
+            else:
+                assert False
+        else:
+            assert parts[1] == "*"
+            new_parts = [eval_2(parts[0]) * eval_2(parts[2])]
+            new_parts += parts[3:]
+        parts = new_parts
+    return parts[-1]
+
+
+data = get_data(__file__)
+
+t1, t2 = 0, 0
+for line in data.splitlines():
+    t1 += eval_1(line)
+    t2 += eval_2(line)
+
+print(t1)
+print(t2)
+assert t2 == 290726428573651

2020/d19.py

@@ -0,0 +1,62 @@
+from lib import get_data
+
+data = get_data(__file__)
+
+rules = {}
+msgs = []
+
+for line in data.splitlines():
+    if len(line.strip()) == 0:
+        continue
+
+    if ":" in line:
+        id, rule = line.split(":")
+        id = int(id)
+
+        branches = [[]]
+        for part in rule.split():
+            if part.startswith('"') and part.endswith('"'):
+                branches = part[1]
+            elif part == "|":
+                assert type(branches) is list
+                branches.append([])
+            else:
+                assert type(branches) is list
+                branches[-1].append(int(part))
+        rules[id] = branches
+    else:
+        msgs.append(line.strip())
+
+
+def matches(xs, rule):
+    if xs == "" and rule == []:
+        return True
+    elif xs == "" or rule == []:
+        return False
+
+    current = rules[rule[0]]
+    if current == xs[0]:
+        return matches(xs[1:], rule[1:])
+    elif type(current) is str:
+        return False
+    elif len(current) >= 1:
+        for ys in current:
+            if matches(xs, ys + rule[1:]):
+                return True
+    return False
+
+
+t = 0
+for m in msgs:
+    if matches(m, rules[0][0]):
+        t += 1
+print(t)
+
+rules[8] = [[42], [42, 8]]
+rules[11] = [[42, 31], [42, 11, 31]]
+
+t = 0
+for m in msgs:
+    if matches(m, rules[0][0]):
+        t += 1
+print(t)

2020/d2.py

@@ -0,0 +1,34 @@
+from lib import get_data
+
+
+def part_1(data):
+    r = 0
+    for line in data.splitlines():
+        pol, pas = line.split(": ")
+        nums, letter = pol.split(" ")
+        lo, hi = list(map(int, nums.split("-")))
+        c = pas.count(letter)
+        if c >= lo and c <= hi:
+            r += 1
+    print(r)
+
+    r = 0
+    for line in data.splitlines():
+        pol, pas = line.split(": ")
+        nums, letter = pol.split(" ")
+        lo, hi = list(map(int, nums.split("-")))
+        c = pas.count(letter)
+        if (pas[lo - 1] == letter or pas[hi - 1] == letter) and not (
+            pas[lo - 1] == letter and pas[hi - 1] == letter
+        ):
+            r += 1
+    print(r)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d20.py

@@ -0,0 +1,169 @@
+from collections import defaultdict
+from lib import get_data, ints
+from math import isqrt
+
+
+data = get_data(__file__)
+
+
+def top(rows):
+    return tuple(rows[0])
+
+
+def bottom(rows):
+    return tuple(rows[-1])
+
+
+def left(rows):
+    return tuple(tuple(row[0] for row in rows))
+
+
+def right(rows):
+    return tuple(tuple(row[-1] for row in rows))
+
+
+def fliph(rows):
+    return tuple(tuple(row[::-1] for row in rows))
+
+
+def flipv(rows):
+    return tuple(rows[::-1])
+
+
+def rot90(rows):
+    return tuple(tuple(row) for row in zip(*rows[::-1]))
+
+
+def rot180(rows):
+    return rot90(rot90(rows))
+
+
+def rot270(rows):
+    return rot90(rot90(rot90(rows)))
+
+
+TOP = 0
+RIGHT = 1
+BOTTOM = 2
+LEFT = 3
+
+
+def all(rows) -> list:
+    return [
+        rows,
+        rot90(rows),
+        rot180(rows),
+        rot270(rows),
+        fliph(rows),
+        flipv(rows),
+        rot90(fliph(rows)),
+        rot90(flipv(rows)),
+        # rot180(fliph(rows)),
+        # rot180(flipv(rows)),
+        # rot270(fliph(rows)),
+        # rot270(flipv(rows)),
+    ]
+
+
+tiles = []
+for p in data.strip().split("\n\n"):
+    lines = p.splitlines()
+    (id,) = ints(lines[0])
+    rowst = tuple(map(tuple, lines[1:]))
+    tiles.append((id, all(rowst)))
+
+
+rights = defaultdict(list)
+bottoms = defaultdict(list)
+
+for id, variants in tiles:
+    for variant in variants:
+        rights[left(variant)].append((id, variant))
+        bottoms[top(variant)].append((id, variant))
+
+num_tiles = len(tiles)
+rows = isqrt(len(tiles))
+
+
+def dfs(id_set, id_list, tiles_used):
+    if len(tiles_used) == num_tiles:
+        return id_list, tiles_used
+
+    i = len(tiles_used)
+    id_variants = None
+    if i < rows:  # first row
+        id_variants = rights[right(tiles_used[i - 1])]
+    elif i % rows == 0:  # first tile in row
+        id_variants = bottoms[bottom(tiles_used[i - rows])]
+    else:
+        id_variants = set(bottoms[bottom(tiles_used[i - rows])])
+        id_variants &= set(rights[right(tiles_used[i - 1])])
+        id_variants = list(id_variants)
+
+    assert id_variants is not None
+
+    for id, variant in id_variants:
+        if id in id_set:
+            continue
+        id_set.add(id)
+        id_list.append(id)
+        tiles_used.append(variant)
+        r = dfs(id_set, id_list, tiles_used)
+        if r is not False:
+            return r
+        tiles_used.pop()
+        id_set.remove(id)
+        id_list.pop()
+    return False, None
+
+
+tiles_used = None
+for id, tile_variants in tiles:
+    for tile in tile_variants:
+        r, tiles_used = dfs(set([id]), [id], [tile])
+        if type(r) is list:
+            print(r[0] * r[-1] * r[rows - 1] * r[-rows])
+            break
+    if tiles_used is not None:
+        break
+else:
+    print("no result")
+    exit(0)
+
+tiles_used = [[tile[x][1:-1] for x in range(1, len(tile) - 1)] for tile in tiles_used]
+
+
+merged_tiles = []
+for i in range(0, rows * rows, rows):
+    for row in range(len(tiles_used[0])):
+        merged_row = []
+        for j in range(rows):
+            merged_row.extend(tiles_used[i + j][row])
+        merged_tiles.append(merged_row)
+
+seemonster = """                  # 
+#    ##    ##    ###
+ #  #  #  #  #  #   """
+
+offsets: list[tuple[int, int]] = []
+for row, line in enumerate(seemonster.splitlines()):
+    for col, c in enumerate(line):
+        if c == "#":
+            offsets.append((row, col))
+
+total_hashes = sum([row.count("#") for row in merged_tiles])
+seemonster_hashes = len(offsets)
+
+max_seemonster_count = 0
+for field in all(merged_tiles):
+    seemonster_count = 0
+    for ri in range(len(field) - 2):
+        for ci in range(len(field[0]) - 19):
+            for ro, co in offsets:
+                if field[ri + ro][ci + co] != "#":
+                    break
+            else:
+                seemonster_count += 1
+    max_seemonster_count = max(max_seemonster_count, seemonster_count)
+
+print(total_hashes - max_seemonster_count * seemonster_hashes)

2020/d21.py

@@ -0,0 +1,50 @@
+from collections import defaultdict
+from lib import get_data
+
+data = get_data(__file__)
+
+algs_to_ings = defaultdict(set)
+ings_counts = defaultdict(int)
+
+for line in data.splitlines():
+    a, b = line.split(" (contains ")
+    ings = a.split(" ")
+    algs = b[:-1].split(", ")
+    for ing in ings:
+        ings_counts[ing] += 1
+
+    for a in algs:
+        if a not in algs_to_ings:
+            algs_to_ings[a] = set(ings)
+        else:
+            algs_to_ings[a] &= set(ings)
+
+
+for ings in algs_to_ings.values():
+    for ing in ings:
+        if ing in ings_counts:
+            del ings_counts[ing]
+t = sum(ings_counts.values())
+print(t)
+
+
+algs_to_ings = {a: list(ing) for a, ing in algs_to_ings.items()}
+
+handled = set()
+while True:
+    to_remove = None
+    for alg, ings in algs_to_ings.items():
+        if len(ings) == 1 and ings[0] not in handled:
+            to_remove = ings[0]
+            break
+    else:
+        break
+    assert to_remove is not None
+    handled.add(to_remove)
+    for ings in algs_to_ings.values():
+        if len(ings) > 1 and to_remove in ings:
+            ings.remove(to_remove)
+
+xs = sorted([(a, i[0]) for a, i in algs_to_ings.items()])
+xs = ",".join([x[1] for x in xs])
+print(xs)

2020/d22.py

@@ -0,0 +1,86 @@
+from collections import deque, defaultdict
+from lib import get_data, ints
+
+data = get_data(__file__)
+
+a, b = data.strip().split("\n\n")
+a = deque(ints(a)[1:])
+b = deque(ints(b)[1:])
+
+while a and b:
+    x, y = a.popleft(), b.popleft()
+    if x > y:
+        a.append(x)
+        a.append(y)
+    elif y > x:
+        b.append(y)
+        b.append(x)
+    else:
+        assert False
+
+
+for p in [a, b]:
+    s = 0
+    for i, c in enumerate(reversed(p)):
+        s += (i + 1) * c
+    if s > 0:
+        print(s)
+
+
+CACHE = {}
+
+
+def play(a, b):
+    if len(a) == 0 or len(b) == 0:
+        return a, b
+
+    s = (tuple(a), tuple(b))
+    if s in CACHE:
+        return CACHE[s]
+
+    seen = set()
+    while a and b:
+        s = (tuple(a), tuple(b))
+        if s in seen:
+            return True, False
+        seen.add(s)
+
+        x, y = a.popleft(), b.popleft()
+        if x <= len(a) and y <= len(b):
+            ar, br = play(deque(list(a)[:x]), deque(list(b)[:y]))
+            if ar:
+                a.append(x)
+                a.append(y)
+            elif br:
+                b.append(y)
+                b.append(x)
+            else:
+                assert False
+        else:
+            if x > y:
+                a.append(x)
+                a.append(y)
+            elif y > x:
+                b.append(y)
+                b.append(x)
+            else:
+                assert False
+
+    s = (tuple(a), tuple(b))
+    if s not in CACHE:
+        CACHE[s] = (a, b)
+
+    return a, b
+
+
+a, b = data.strip().split("\n\n")
+a = deque(ints(a)[1:])
+b = deque(ints(b)[1:])
+a, b = play(a, b)
+
+for p in [a, b]:
+    s = 0
+    for i, c in enumerate(reversed(p)):
+        s += (i + 1) * c
+    if s > 0:
+        print(s)

2020/d23.py

@@ -0,0 +1,73 @@
+from lib import get_data
+
+data = get_data(__file__)
+
+cups = list(map(int, list(data.strip())))
+min_label = min(cups)
+max_label = max(cups)
+
+cmap = {}
+for i in range(len(cups)):
+    cmap[cups[i]] = cups[(i + 1) % len(cups)]
+
+cc = cups[0]
+for _ in range(100):
+    a = cmap[cc]
+    b = cmap[a]
+    c = cmap[b]
+
+    cmap[cc] = cmap[c]
+
+    dest = cc - 1
+    while dest in {a, b, c} or dest < min_label:
+        dest = dest - 1
+        if dest < min_label:
+            dest = max_label
+
+    cmap[c] = cmap[dest]
+    cmap[dest] = a
+
+    cc = cmap[cc]
+
+s = ""
+cup = cmap[1]
+while cup != 1:
+    s += str(cup)
+    cup = cmap[cup]
+print(s)
+
+cups = list(map(int, list(data.strip())))
+current = max(cups) + 1
+while len(cups) != 1_000_000:
+    cups.append(current)
+    current += 1
+
+min_label = min(cups)
+max_label = max(cups)
+cmap = {}
+for i in range(len(cups)):
+    cmap[cups[i]] = cups[(i + 1) % len(cups)]
+
+cc = cups[0]
+for _ in range(10_000_000):
+    a = cmap[cc]
+    b = cmap[a]
+    c = cmap[b]
+
+    cmap[cc] = cmap[c]
+
+    dest = cc - 1
+    while dest in {a, b, c} or dest < min_label:
+        dest = dest - 1
+        if dest < min_label:
+            dest = max_label
+
+    cmap[c] = cmap[dest]
+    cmap[dest] = a
+
+    cc = cmap[cc]
+
+a = cmap[1]
+b = cmap[a]
+
+print(a * b)

2020/d24.py

@@ -0,0 +1,59 @@
+from lib import get_data, add2
+from collections import defaultdict
+
+DIRS = {
+    "e": (0, 2),
+    "w": (0, -2),
+    "se": (1, 1),
+    "sw": (1, -1),
+    "nw": (-1, -1),
+    "ne": (-1, 1),
+}
+
+data = get_data(__file__)
+
+tiles_black = set()
+
+for row in data.splitlines():
+    row = row.strip()
+    i = 0
+    pos = (0, 0)
+    while i < len(row):
+        d = None
+        if row[i] in DIRS:
+            d = DIRS[row[i]]
+            i += 1
+        elif "".join(row[i : i + 2]) in DIRS:
+            d = DIRS["".join(row[i : i + 2])]
+            i += 2
+        else:
+            assert False
+        assert d is not None
+        pos = add2(pos, d)
+    if pos in tiles_black:
+        tiles_black.remove(pos)
+    else:
+        tiles_black.add(pos)
+
+print(len(tiles_black))
+
+for _ in range(100):
+    nbs = defaultdict(int)
+    for bt in tiles_black:
+        for d in DIRS.values():
+            nb = add2(bt, d)
+            nbs[nb] += 1
+    new_tiles_black = set()
+    for pos, count in nbs.items():
+        if pos in tiles_black:
+            if count == 0 or count > 2:
+                pass
+            else:
+                new_tiles_black.add(pos)
+        else:
+            if count == 2:
+                new_tiles_black.add(pos)
+
+    tiles_black = new_tiles_black
+
+print(len(tiles_black))

2020/d25.py

@@ -0,0 +1,32 @@
+from lib import get_data, ints
+
+data = get_data(__file__)
+a, b = ints(data)
+
+v = 1
+subject_number = 7
+al, bl = None, None
+
+for loop in range(100_000_000):
+    v *= subject_number
+    v %= 20201227
+    if al is None and v == a:
+        al = loop + 1
+    if bl is None and v == b:
+        bl = loop + 1
+
+    if al and bl:
+        break
+
+assert al is not None
+assert bl is not None
+# print(al, bl)
+
+v = 1
+subject_number = b
+for _ in range(al):
+    v *= subject_number
+    v %= 20201227
+
+print(v)
+

2020/d3.py

@@ -0,0 +1,33 @@
+from lib import get_data, Grid2D
+
+
+def part_1(data):
+    g = Grid2D(data)
+
+    pos = (0, 0)
+    r = 0
+    while pos[0] < g.n_rows:
+        if g[pos] == "#":
+            r += 1
+        pos = (pos[0] + 1, (pos[1] + 3) % g.n_cols)
+    print(r)
+
+    fr = 1
+    for dr, dc in [(1, 1), (1, 3), (1, 5), (1, 7), (2, 1)]:
+        pos = (0, 0)
+        r = 0
+        while pos[0] < g.n_rows:
+            if g[pos] == "#":
+                r += 1
+            pos = (pos[0] + dr, (pos[1] + dc) % g.n_cols)
+        fr *= r
+    print(fr)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d4.py

@@ -0,0 +1,107 @@
+from lib import get_data
+
+required = [
+    "byr",
+    "iyr",
+    "eyr",
+    "hgt",
+    "hcl",
+    "ecl",
+    "pid",
+]
+
+
+# hgt (Height) - a number followed by either cm or in:
+#
+#     If cm, the number must be at least 150 and at most 193.
+#     If in, the number must be at least 59 and at most 76.
+
+
+def part_1(data):
+    passwords = [""]
+    for line in data.splitlines():
+        if line.strip() == "":
+            passwords.append("")
+        else:
+            passwords[-1] = passwords[-1] + " " + line.strip()
+
+    valid = 0
+    for pw in passwords:
+        for r in required:
+            if r not in pw:
+                break
+        else:
+            valid += 1
+    print(valid)
+
+    kws = []
+    for pw in passwords:
+        d = {}
+        for word in pw.split():
+            key, value = word.split(":")
+            d[key] = value
+        kws.append(d)
+
+    valid = 0
+    for kw in kws:
+        for r in required:
+            if r not in kw:
+                break
+            match r:
+                case "hgt":
+                    v = int(kw[r][:-2])
+                    if kw[r].endswith("cm"):
+                        if v < 150 or v > 193:
+                            break
+                    elif kw[r].endswith("in"):
+                        if v < 59 or v > 76:
+                            break
+                    else:
+                        break
+                case "byr":
+                    v = int(kw[r])
+                    if v < 1920 or v > 2002:
+                        break
+                case "iyr":
+                    v = int(kw[r])
+                    if v < 2010 or v > 2020:
+                        break
+                case "eyr":
+                    v = int(kw[r])
+                    if v < 2020 or v > 2030:
+                        break
+                case "hcl":
+                    v = kw[r]
+                    if len(v) != 7 or not v.startswith("#"):
+                        break
+                    try:
+                        int(v.replace("#", ""), 16)
+                    except ValueError:
+                        break
+                case "pid":
+                    v = kw[r]
+                    if len(v) != 9:
+                        break
+                    try:
+                        int(v, 10)
+                    except ValueError:
+                        break
+                case "ecl":
+                    v = kw[r]
+                    if not v in ["amb", "blu", "brn", "gry", "grn", "hzl", "oth"]:
+                        break
+                case _:
+                    assert False
+
+        else:
+            valid += 1
+    print(valid)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d5.py

@@ -0,0 +1,40 @@
+from lib import get_data
+
+
+def part_1(data):
+    rs = []
+    for line in data.splitlines():
+        rl, ru = 0, 127
+        cl, cu = 0, 7
+        for c in line.strip():
+            rh = (ru - rl) // 2
+            ch = (cu - cl) // 2
+            if c == "B":
+                rl = rl + rh + 1
+            elif c == "F":
+                ru = rl + rh
+            elif c == "R":
+                cl = cl + ch + 1
+            elif c == "L":
+                cu = cl + ch
+            else:
+                assert False
+        assert rl == ru
+        assert cl == cu
+        r_new = rl * 8 + cl
+        rs.append(r_new)
+
+    print(max(rs))
+    rs = sorted(rs)
+    for i in range(len(rs) - 1):
+        if rs[i] + 1 != rs[i + 1]:
+            print(rs[i] + 1)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d6.py

@@ -0,0 +1,24 @@
+from lib import get_data
+
+
+def part_1(data):
+    r1, r2 = 0, 0
+    for group in data.split("\n\n"):
+        r1 += len(set(group.replace("\n", "")))
+
+        s = set(group.splitlines()[0])
+        for line in group.splitlines():
+            s &= set(line)
+        r2 += len(s)
+
+    print(r1)
+    print(r2)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d7.py

@@ -0,0 +1,47 @@
+from lib import get_data
+
+
+def part_1(data):
+    bags = {}
+    for line in data.splitlines():
+        left, right = line.split(" contain ")
+        lb = " ".join(left.split()[:2])
+        rbs = right.replace(" bag", "").replace(" bags", "").replace(".", "").split(",")
+        if "no others" in rbs:
+            rbs = []
+        else:
+            rbs = [[int(v.split()[0]), " ".join(v.split()[1:])] for v in rbs]
+        assert lb not in bags
+        bags[lb] = rbs
+
+    for lb, rbs in bags.items():
+        for t in rbs:
+            if t[0] > 1:
+                t[1] = t[1][:-1]
+
+    can_hold = set(["shiny gold"])
+    can_hold_count = -1
+    while can_hold_count != len(can_hold):
+        can_hold_count = len(can_hold)
+        for lb, rbs in bags.items():
+            for _, bag_color in rbs:
+                if bag_color in can_hold:
+                    can_hold.add(lb)
+    print(len(can_hold) - 1)
+
+    def count(color):
+        r = 1  # the bag itself
+        for c, icolor in bags[color]:
+            r += c * count(icolor)
+        return r
+
+    print(count("shiny gold") - 1)
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d8.py

@@ -0,0 +1,71 @@
+from lib import get_data, str_to_ints
+
+
+def part_1(data):
+    insts = data.splitlines()
+    acc = 0
+    i = 0
+    seen = set()
+
+    while i < len(insts) and i not in seen:
+        inst = insts[i]
+        seen.add(i)
+        if inst.startswith("acc"):
+            (v,) = str_to_ints(inst)
+            acc += v
+            i += 1
+        elif inst.startswith("jmp"):
+            (v,) = str_to_ints(inst)
+            i += v
+        elif inst.startswith("nop"):
+            i += 1
+        else:
+            assert False
+
+    print(acc)
+
+    for j in range(len(insts)):
+
+        if "jmp" in insts[j]:
+            insts[j] = insts[j].replace("jmp", "nop")
+        elif "nop" in insts[j]:
+            insts[j] = insts[j].replace("nop", "jmp")
+        else:
+            continue
+
+        i = 0
+        acc = 0
+        seen = set()
+        while i < len(insts) and i not in seen:
+            inst = insts[i]
+            seen.add(i)
+            if inst.startswith("acc"):
+                (v,) = str_to_ints(inst)
+                acc += v
+                i += 1
+            elif inst.startswith("jmp"):
+                (v,) = str_to_ints(inst)
+                i += v
+            elif inst.startswith("nop"):
+                i += 1
+            else:
+                assert False
+
+        if not i in seen:
+            print(acc)
+
+        if "jmp" in insts[j]:
+            insts[j] = insts[j].replace("jmp", "nop")
+        elif "nop" in insts[j]:
+            insts[j] = insts[j].replace("nop", "jmp")
+        else:
+            continue
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/d9.py

@@ -0,0 +1,33 @@
+from lib import get_data
+
+
+def part_1(data):
+    target = 0
+    xs = list(map(int, data.splitlines()))
+    for i in range(25, len(xs)):
+        x = xs[i]
+        good = False
+        for j in range(i - 25, i):
+            for k in range(j, i):
+                if xs[j] + xs[k] == x:
+                    good = True
+        if not good:
+            print(x)
+            target = x
+            break
+
+    for i in range(len(xs)):
+        for j in range(i + 1, len(xs)):
+            if sum(xs[i : j + 1]) == target:
+                r = xs[i : j + 1]
+                print(min(r) + max(r))
+                return
+
+
+def main():
+    data = get_data(__file__)
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2020/lib.py

@@ -0,0 +1 @@
+../lib.py

2020/monitor.py

@@ -0,0 +1 @@
+../monitor.py

2021/d1.py

@@ -0,0 +1,20 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__)
+xs = ints(data)
+
+t = 0
+for a, b in zip(xs, xs[1:]):
+    if b > a:
+        t += 1
+print(t)
+
+t = 0
+prev_sum = 10**12
+for i in range(len(xs) - 2):
+    s = sum(xs[i : i + 3])
+    if s > prev_sum:
+        t += 1
+    prev_sum = s
+print(t)

2021/d10.py

@@ -0,0 +1,63 @@
+from lib import get_data
+
+data = get_data(__file__).strip()
+
+OPEN = "([{<"
+CLOSE = ")]}>"
+
+
+def part1(line):
+    score = {
+        ")": 3,
+        "]": 57,
+        "}": 1197,
+        ">": 25137,
+    }
+    stack = []
+    for c in line:
+        if c in OPEN:
+            stack.append(OPEN.index(c))
+        elif c in CLOSE:
+            ci = CLOSE.index(c)
+            if stack and stack[-1] == ci:
+                stack.pop()
+                continue
+            else:
+                return score[c]
+        else:
+            assert False
+    return 0
+
+
+def part2(line):
+    stack = []
+    for c in line:
+        if c in OPEN:
+            stack.append(OPEN.index(c))
+        elif c in CLOSE:
+            ci = CLOSE.index(c)
+            if stack and stack[-1] == ci:
+                stack.pop()
+                continue
+            else:
+                assert False
+        else:
+            assert False
+    score = 0
+    for v in reversed(stack):
+        score *= 5
+        score += v + 1
+    return score
+
+
+s1 = 0
+s2s = []
+for line in data.splitlines():
+    s = part1(line)
+    if s == 0:
+        s2s.append(part2(line))
+    s1 += s
+
+print(s1)
+s2 = sorted(s2s)[len(s2s) // 2]
+print(s2)

2021/d11.py

@@ -0,0 +1,37 @@
+from lib import get_data
+from lib import Grid2D
+
+data = get_data(__file__).strip()
+g = Grid2D(data)
+
+flashes_100 = 0
+all_flash_round = None
+for i in range(10**9):
+    for row in range(g.n_rows):
+        for col in range(g.n_cols):
+            g[(row, col)] = str(int(g[(row, col)]) + 1)
+
+    has_flashed = set()
+    more_flashes = True
+    while more_flashes:
+        more_flashes = False
+        for row in range(g.n_rows):
+            for col in range(g.n_cols):
+                level = int(g[(row, col)])
+                if level > 9 and (row, col) not in has_flashed:
+                    more_flashes = True
+                    for nb in g.neighbors_adj((row, col)):
+                        g[nb] = str(int(g[nb]) + 1)
+                    has_flashed.add((row, col))
+    for oct in has_flashed:
+        g[oct] = "0"
+
+    if i < 100:
+        flashes_100 += len(has_flashed)
+
+    if len(has_flashed) == g.n_rows * g.n_cols:
+        all_flash_round = i + 1
+        break
+
+print(flashes_100)
+print(all_flash_round)

2021/d12.py

@@ -0,0 +1,56 @@
+from lib import get_data
+from lib import Grid2D
+from lib import ints
+from collections import deque
+from collections import defaultdict
+
+data = get_data(__file__).strip()
+g = defaultdict(list)
+
+
+for line in data.splitlines():
+    a, b = line.strip().split("-")
+    g[a].append(b)
+    g[b].append(a)
+
+
+def no_doubles(path):
+    path = [p for p in path if p.islower()]
+    return len(path) == len(set(path))
+
+
+for part in [1, 2]:
+    start = ("start", ())
+    visited = set()
+    queue = deque([start])
+
+    total = 0
+    while queue:
+        vertex = queue.popleft()
+        if vertex in visited:
+            continue
+        visited.add(vertex)
+
+        current, path = vertex
+
+        neighbors = []
+        for neighbor in g[current]:
+            if neighbor == "end":
+                total += 1
+            elif neighbor == "start":
+                continue
+            elif neighbor.islower():
+                if neighbor not in path or (part == 2 and no_doubles(path)):
+                    new_path = tuple(list(path) + [neighbor])
+                    nb = (neighbor, new_path)
+                    if nb not in visited:
+                        queue.append(nb)
+            elif neighbor.isupper():
+                new_path = tuple(list(path) + [neighbor])
+                nb = (neighbor, new_path)
+                if nb not in visited:
+                    queue.append(nb)
+            else:
+                assert False
+
+    print(total)

2021/d13.py

@@ -0,0 +1,51 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__).strip()
+
+
+def print_from_xy(xs):
+    x_min = min(v[0] for v in xs)
+    x_max = max(v[0] for v in xs)
+    y_min = min(v[1] for v in xs)
+    y_max = max(v[1] for v in xs)
+    for y in range(y_min, y_max + 1):
+        row = ""
+        for x in range(x_min, x_max + 1):
+            if (x, y) in xs:
+                row += "#"
+            else:
+                row += " "
+        print(row)
+
+
+p1, p2 = data.split("\n\n")
+xs = set([tuple(ints(line)) for line in p1.splitlines()])
+
+folds = []
+for line in p2.splitlines():
+    d = "x" if "x=" in line else "y"
+    (n,) = ints(line)
+    folds.append((d, n))
+
+
+first = None
+for d, n in folds:
+    if d == "x":
+        to_move = [(x, y) for (x, y) in xs if x > n]
+        for x, y in to_move:
+            xs.remove((x, y))
+            new_x = n - (x - n)
+            xs.add((new_x, y))
+    elif d == "y":
+        to_move = [(x, y) for (x, y) in xs if y > n]
+        for x, y in to_move:
+            xs.remove((x, y))
+            new_y = n - (y - n)
+            xs.add((x, new_y))
+    else:
+        assert False
+    first = first or len(xs)
+
+print(first)
+print_from_xy(xs)

2021/d14.py

@@ -0,0 +1,43 @@
+from lib import get_data
+from itertools import pairwise
+from collections import defaultdict
+
+data = get_data(__file__)
+orig_t, p2 = data.split("\n\n")
+
+pairs = {}
+for line in p2.splitlines():
+    ls, rs = line.split(" -> ")
+    assert ls not in pairs
+    pairs[ls] = rs
+
+for steps in [10, 40]:
+    t = str(orig_t)
+    start_letter = t[0]
+    end_letter = t[-1]
+    td = defaultdict(int)
+    for a, b in pairwise(t):
+        td[a + b] += 1
+
+    for _ in range(steps):
+        ntd = defaultdict(int)
+        for pair, count in td.items():
+            if pair in pairs:
+                a, b = pair
+                c = pairs[pair]
+                ntd[a + c] += count
+                ntd[c + b] += count
+            else:
+                ntd[pair] += count
+        td = ntd
+
+    counts = defaultdict(int)
+    for (a, b), count in td.items():
+        counts[a] += count
+        counts[b] += count
+    counts = {k: v // 2 for k, v in counts.items()}
+    counts[start_letter] += 1
+    counts[end_letter] += 1
+
+    r = max(counts.values()) - min(counts.values())
+    print(r)

2021/d15.py

@@ -0,0 +1,83 @@
+from lib import get_data
+from lib import Grid2D
+import heapq
+
+data = get_data(__file__)
+
+
+def new_data(data, repeat=5):
+    new_lines = []
+    for line in data.splitlines():
+        new_line = str(line)
+        for i in range(len(line) * repeat):
+            ni = i - len(line)
+            if ni < 0:
+                continue
+            nc = int(new_line[ni]) + 1
+            if nc == 10:
+                nc = 1
+            new_line += str(nc)
+        new_lines.append(new_line)
+
+    for i in range(len(data.splitlines()) * repeat):
+        ni = i - len(data.splitlines())
+        if ni < 0:
+            continue
+        line = list(new_lines[ni])
+        for i in range(len(line)):
+            nc = int(line[i]) + 1
+            if nc == 10:
+                nc = 1
+            line[i] = str(nc)
+        line = "".join(line)
+        new_lines.append(line)
+
+    data = "\n".join(new_lines)
+    return data
+
+
+big_data = new_data(data)
+
+for data in [data, big_data]:
+    g = Grid2D(data)
+
+    def dist(n1, n2):
+        """cost from node to node"""
+        if n1 == 0:
+            return 0
+        return int(g[n2])
+
+    def h(node):
+        """heuristic function (never overestimate)"""
+        return abs(g.n_rows - 1 - node[0]) + abs(g.n_cols - 1 - node[1])
+
+    def is_goal(node):
+        return node == (g.n_rows - 1, g.n_cols - 1)
+
+    def neighbors(node):
+        return list(g.neighbors_ort(node))
+
+    starts = [(0, 0)]
+    open_set = []
+    g_score = {}
+    cost = None
+
+    for start in starts:
+        heapq.heappush(open_set, (h(start), start))
+        g_score[start] = dist(0, start)
+
+    while open_set:
+        current_f_score, current = heapq.heappop(open_set)
+        if is_goal(current):
+            assert current_f_score == g_score[current]
+            cost = g_score[current]
+            break
+
+        for neighbor in neighbors(current):
+            tentative_g_score = g_score[current] + dist(current, neighbor)
+            if neighbor not in g_score or tentative_g_score < g_score[neighbor]:
+                g_score[neighbor] = tentative_g_score
+                f_score = g_score[neighbor] + h(neighbor)
+                heapq.heappush(open_set, (f_score, neighbor))
+
+    print(cost)

2021/d16.py

@@ -0,0 +1,85 @@
+from lib import get_data
+
+
+data = get_data(__file__)
+
+bs = ""
+for c in data.strip():
+    b = bin(int(c, 16))[2:]
+    b = "0" * (4 - len(b)) + b
+    bs += b
+
+total_v = 0
+
+
+def parse(bs: str, i: int):
+    v = int(bs[i : i + 3], 2)
+    global total_v
+    total_v += v
+    i += 3
+    t = int(bs[i : i + 3], 2)
+    i += 3
+
+    # print(v, t)
+    if t == 4:
+        lv = ""
+        while True:
+            seg = bs[i : i + 5]
+            lv += seg[1:]
+            i += 5
+            if seg[0] == "0":
+                break
+        lv = int(lv, 2)
+        return i, lv
+
+    vs = []
+    if bs[i] == "0":
+        # total length of bits
+        i += 1
+        bits = int(bs[i : i + 15], 2)
+        i += 15
+        i_max = i + bits
+        while True:
+            i, v = parse(bs, i)
+            vs.append(v)
+            if i >= i_max:
+                break
+    elif bs[i] == "1":
+        # number of sub-packets
+        i += 1
+        num_sub = int(bs[i : i + 11], 2)
+        i += 11
+        vs = []
+        for _ in range(num_sub):
+            i, v = parse(bs, i)
+            vs.append(v)
+    else:
+        assert False
+
+    if t == 0:
+        return i, sum(vs)
+    elif t == 1:
+        x = 1
+        for v in vs:
+            x *= v
+        return i, x
+    elif t == 2:
+        return i, min(vs)
+    elif t == 3:
+        return i, max(vs)
+    elif t == 5:
+        assert len(vs) == 2
+        return i, 1 if vs[0] > vs[1] else 0
+    elif t == 6:
+        assert len(vs) == 2
+        return i, 1 if vs[0] < vs[1] else 0
+    elif t == 7:
+        assert len(vs) == 2
+        return i, 1 if vs[0] == vs[1] else 0
+    else:
+        assert False
+
+
+p2 = parse(bs, 0)[1]
+print(total_v)
+print(p2)

2021/d17.py

@@ -0,0 +1,35 @@
+from lib import get_data
+from lib import ints
+
+
+data = get_data(__file__)
+x_min, x_max, y_min, y_max = ints(data)
+
+
+def simulate(x, y, vx, vy):
+    height_max = 0
+    while x <= x_max and y >= y_min:
+        height_max = max(y, height_max)
+        if x_min <= x <= x_max and y_min <= y <= y_max:
+            return True, height_max
+
+        x += vx
+        y += vy
+        if vx != 0:
+            vx = vx - 1 if vx > 0 else vx + 1
+        vy -= 1
+    return False, 0
+
+
+height_max = 0
+total = set()
+for vx in range(1, 2000):
+    for vy in range(-2000, 2000):
+        in_target, height = simulate(0, 0, vx, vy)
+        if in_target:
+            total.add((vx, vy))
+        if in_target and height > height_max:
+            height_max = height
+
+print(height_max)
+print(len(total))

2021/d18.py

@@ -0,0 +1,115 @@
+from lib import get_data
+from math import ceil, floor
+from itertools import combinations
+
+data = """[[[0,[5,8]],[[1,7],[9,6]]],[[4,[1,2]],[[1,4],2]]]
+[[[5,[2,8]],4],[5,[[9,9],0]]]
+[6,[[[6,2],[5,6]],[[7,6],[4,7]]]]
+[[[6,[0,7]],[0,9]],[4,[9,[9,0]]]]
+[[[7,[6,4]],[3,[1,3]]],[[[5,5],1],9]]
+[[6,[[7,3],[3,2]]],[[[3,8],[5,7]],4]]
+[[[[5,4],[7,7]],8],[[8,3],8]]
+[[9,3],[[9,9],[6,[4,9]]]]
+[[2,[[7,7],7]],[[5,8],[[9,3],[0,2]]]]
+[[[[5,2],5],[8,[3,7]]],[[5,[7,5]],[4,4]]]"""
+data = get_data(__file__)
+
+
+def parse(line):
+    xs = list(line)
+    for i in range(len(xs)):
+        try:
+            xs[i] = int(xs[i])
+        except ValueError:
+            pass
+    assert line == "".join(map(str, xs))
+    return xs
+
+
+def reduce(xs):
+    reduced, nesting = False, 0
+    for i in range(len(xs)):
+        c = xs[i]
+        if c == "[" and nesting == 4 and not reduced:
+            lhs, rhs = xs[i + 1], xs[i + 3]
+            if not (type(lhs) is int and type(rhs) is int):
+                continue
+            xs = xs[:i] + [0] + xs[i + 5 :]
+
+            for j in range(i - 1, -1, -1):
+                if type(xs[j]) is int:
+                    xs[j] += lhs
+                    break
+
+            for j in range(i + 1, len(xs)):
+                if type(xs[j]) is int:
+                    xs[j] += rhs
+                    break
+            reduced = True
+            break
+        elif c == "[":
+            nesting += 1
+        elif c == "]":
+            nesting -= 1
+
+    if not reduced:
+        for i in range(len(xs)):
+            c = xs[i]
+            if type(c) is int and c >= 10:
+                p = [floor(c / 2), ceil(c / 2)]
+                xs = xs[:i] + ["[", p[0], ",", p[1], "]"] + xs[i + 1 :]
+                reduced = True
+                break
+    return xs
+
+
+def restore(xs):
+    return "".join(map(str, xs))
+
+
+assert restore(reduce(parse("[[[[[9,8],1],2],3],4]"))) == "[[[[0,9],2],3],4]"
+assert restore(reduce(parse("[7,[6,[5,[4,[3,2]]]]]"))) == "[7,[6,[5,[7,0]]]]"
+assert (
+    restore(reduce(parse("[[3,[2,[1,[7,3]]]],[6,[5,[4,[3,2]]]]]")))
+    == "[[3,[2,[8,0]]],[9,[5,[4,[3,2]]]]]"
+)
+assert (
+    restore(reduce(parse("[[3,[2,[8,0]]],[9,[5,[4,[3,2]]]]]")))
+    == "[[3,[2,[8,0]]],[9,[5,[7,0]]]]"
+)
+
+
+def add(a, b):
+    s = ["["] + a + [","] + b + ["]"]
+    while True:
+        ns = reduce(s)
+        if s == ns:
+            break
+        s = ns
+    return s
+
+
+a = "[[[[4,3],4],4],[7,[[8,4],9]]]"
+b = "[1,1]"
+assert restore(add(parse(a), parse(b))) == "[[[[0,7],4],[[7,8],[6,0]]],[8,1]]"
+
+lines = list(data.splitlines())
+s = parse(lines[0].strip())
+for line in lines[1:]:
+    s = add(s, parse(line.strip()))
+
+
+def get_mag(xs):
+    if type(xs) is int:
+        return xs
+    return get_mag(xs[0]) * 3 + get_mag(xs[1]) * 2
+
+
+print(get_mag(eval(restore(s))))
+
+lines = list(data.splitlines())
+m = 0
+for a, b in combinations(lines, 2):
+    m = max(m, get_mag(eval(restore(add(parse(a), parse(b))))))
+    m = max(m, get_mag(eval(restore(add(parse(b), parse(a))))))
+print(m)

2021/d19.py

@@ -0,0 +1,121 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+from itertools import permutations, product
+
+V3 = tuple[int, int, int]
+
+data = get_data(__file__)
+scanners = []
+for block in data.split("\n\n"):
+    scanner = []
+    for line in block.splitlines()[1:]:
+        a, b, c = ints(line)
+        scanner.append((a, b, c))
+    scanners.append(scanner)
+
+
+def rotate(vi: V3) -> list[V3]:
+    r = []
+    for p in permutations(vi):
+        for f in product([1, -1], repeat=3):
+            v = tuple([a * b for a, b in zip(p, f)])
+            r.append(v)
+    return r
+
+
+assert len(rotate((8, 0, 7))) == 48
+
+
+def sub(a: V3, b: V3) -> V3:
+    return a[0] - b[0], a[1] - b[1], a[2] - b[2]
+
+
+def add(a: V3, b: V3) -> V3:
+    return a[0] + b[0], a[1] + b[1], a[2] + b[2]
+
+
+def relative(scanner: list[V3]):
+    d = defaultdict(list)
+    for i in range(len(scanner)):
+        for j in range(i + 1, len(scanner)):
+            for ii, jj in [(i, j), (j, i)]:
+                a, b = scanner[ii], scanner[jj]
+                delta = sub(a, b)
+                d[delta].append((a, b))
+    return d
+
+
+def overlap(scanner_1, scanner_2):
+    expected_overlaps = 15
+    r1 = relative(scanner_1)
+    scanners_2 = []
+    for scanner in list(zip(*list(map(rotate, scanner_2)))):
+        os = set()
+        r2 = relative(scanner)
+        # number of bacon pairs that have the same offset
+        t = sum(1 for k1 in r1.keys() if k1 in r2)
+        if t >= expected_overlaps:
+            for k1, v1 in r1.items():
+                if k1 in r2:
+                    ((abs1, abs2),) = v1
+                    ((rel1, rel2),) = r2[k1]
+                    os.add(sub(abs1, rel1))
+                    os.add(sub(abs2, rel2))
+            if len(os) == 1:
+                # found the right orientation for scanner_2
+                scanners_2.append((os.pop(), scanner))
+            else:
+                r2 = None
+        else:
+            r2 = None
+
+    if len(scanners_2) == 0:
+        return None
+    ((orig_2, scanner_2_rel),) = scanners_2
+    scanner_2_abs = [add(orig_2, b) for b in scanner_2_rel]
+    return orig_2, scanner_2_abs
+
+
+origs = [(0, 0, 0)]
+todo = set(range(len(scanners)))
+done = set([0]) if 0 in todo else set([todo.pop()])
+todo.discard(0)
+while todo:
+    for i in range(len(scanners)):
+        for j in range(len(scanners)):
+            if i == j:
+                continue
+            if i not in done:
+                continue
+            if j in done:
+                continue
+            r = overlap(scanners[i], scanners[j])
+
+            if r is None:
+                continue
+            o, s2 = r
+            origs.append(o)
+            no = len(set(scanners[i]).intersection(s2))
+            if no >= 12:
+                scanners[j] = s2
+                done.add(j)
+                todo.discard(j)
+                # print(f"{i} < {no} > {j} at {o}")
+
+
+all = []
+for s in scanners:
+    all += s
+print(len(set(all)))
+
+
+def mdist(a, b):
+    return sum(abs(aa - bb) for aa, bb in zip(a, b))
+
+
+m = 0
+for i in range(len(origs)):
+    for j in range(i + 1, len(origs)):
+        m = max(m, mdist(origs[i], origs[j]))
+print(m)

2021/d2.py

@@ -0,0 +1,24 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__)
+
+aim, h2, d2 = 0, 0, 0
+h, d = 0, 0
+for line in data.splitlines():
+    (v,) = ints(line)
+    if "forward" in line:
+        h2 += v
+        d2 += aim * v
+        h += v
+    elif "down" in line:
+        aim += v
+        d += v
+    elif "up" in line:
+        aim -= v
+        d -= v
+    else:
+        assert False
+
+print(h * d)
+print(h2 * d2)