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
-    elif valid_count == 2:
-        break
-print(data)
+        if part_1 and valid_count == 1:
+            print(data)
+        elif valid_count == 2:
+            print(data)
+            break

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:
+                t += st
+        else:
+            for o in obj.values():
+                t += xsum(o, part_2)
+    elif type(obj) is str:
+        pass
     else:
-        r += d
-    return r
+        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()
-
-part_1 = True
-if part_1:
-    a = 0
-    for line in data:
-        l, w, h = list(map(int, line.split("x")))
-        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")))
-        sd = min([2 * (l + w), 2 * (w + h), 2 * (h + l)])
-        a +=  sd + (l * w * h)
+data = get_data(__file__)
 
+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
+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:
-        d = DIRS[c]
-        pos = pos[0] + d[0], pos[1] + d[1]
-        poss.add(pos)
+for c in data:
+    d = DIRS[c]
+    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

@@ -1,22 +1,15 @@
-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):
-    text = data + str(i)
-    md5_hash = hashlib.md5(text.encode()).hexdigest()
-    for c in md5_hash[:digits]:
-        if c != "0":
+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]:
+            if c != "0":
+                break
+        else:
+            print(i)
             break
-    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():
-        vc = 0
-        for c in line:
-            if c in "aoeui":
-                vc += 1
-        if vc < 3:
-            continue
 
-        prev = None
-        for c in line:
-            if c == prev:
-                break
-            prev = c
-        else:
-            continue
+def is_nice(line):
+    # It contains at least three vowels (aeiou only), like aei, xazegov, or aeiouaeiouaeiou.
+    vc = 0
+    for v in "aeiou":
+        vc += line.count(v)
+    if vc < 3:
+        return False
 
-        contains = False
-        ss = ["ab", "cd", "pq", "xy"]
-        for s in ss:
-            if s in line:
-                contains = True
+    # 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:
+        return False
 
-        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
+    # 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
 
-        for i in range(0, len(line) - 2):
-            if line[i] == line[i + 2]:
-                break
-        else:
-            continue
-        res += 1
-    print(res)
+
+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:
-    for line in data.splitlines():
-        lhs, rhs = line.split(" -> ")
-        if part_2 and rhs == "b":
-            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]
-
-            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
+def run(wires={}):
+    def get(a):
+        try:
+            return int(a)
+        except ValueError:
+            pass
+        if a in wires:
+            return wires[a]
         else:
-            try:
-                lhs = int(lhs)
-                gates[rhs] = lhs
-            except ValueError:
-                if lhs in gates:
-                    gates[rhs] = gates[lhs]
+            return None
 
-print(gates["a"])
+    while "a" not in wires:
+        for line in data.splitlines():
+            lhs, rhs = line.split(" -> ")
+            if rhs in wires:
+                continue
+            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
+
+
+a = run()["a"]
+print(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():
-        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():
-        ori += len(line)
-        line = line.replace("\\", "\\\\")
-        line = line.replace("\"", "\\\"")
-        enc += len(line) + 2
-    print(enc - ori)
+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)
+
+ori, enc = 0, 0
+for line in data.splitlines():
+    ori += len(line)
+    line = line.replace("\\", "\\\\")
+    line = line.replace('"', '\\"')
+    enc += len(line) + 2
+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/d19.py

@@ -2,40 +2,133 @@ from lib import get_data, str_to_ints
 import d16
 
 
-def part_1(data):
+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] = 1  # part 2
+    regs[0] = reg_zero_init
 
     insts = []
     for line in data.splitlines():
         if line.startswith("#"):
-            ip, = str_to_ints(line)
+            (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])
-        # if inst[1:] == [3, 1, 3]:
-        #     regs[3] = regs[1]
-        #     regs[4] = regs[1]
         f(regs, *inst[1:])
         regs[ip] += 1
-        print(regs, regs[-1] + 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))

2019/d12.py

@@ -1,4 +1,5 @@
 from lib import get_data, str_to_ints
+from math import lcm
 
 
 def freeze(coords, velos):
@@ -40,7 +41,40 @@ def part_1(data):
 
 
 def part_2(data):
-    raise Exception("TBD")
+    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():

2019/d16.py

@@ -40,7 +40,7 @@ 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)
+        # print(round)
 
         pattern_value = pattern[((i + 1) // (round + 1)) % len(pattern)]
         if pattern_value == 0:
@@ -53,8 +53,6 @@ def phase_with_offset(digits_in, pattern, offset):
                 out += pattern_value * sum(
                     digits_in[i : min(i + 1 + round, len(digits_in))]
                 )
-                # for j in range(i, min(i + 1 + round, len(digits_in))):
-                #     out += (pattern_value * digits_in[j])
             i += round + 1
 
         out = abs(out) % 10
@@ -71,16 +69,33 @@ def part_1(data):
         input = phase_with_offset(input, pattern, 0)
     print("".join(map(str, input[:8])))
 
-    input = list(map(int, (data.strip()))) * 10_000
-    offset = int("".join(map(str, input[:7]))) - 200
+    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])))
 
-    for i in range(100):
-        print(i)
-        input = phase_with_offset(input, pattern, offset)
-    print(input)
-
-    return
+    # 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.

2019/d17.py

@@ -51,9 +51,11 @@ def find_path(g):
                 path += "R"
                 dir = DIRS[(DIRS.index(dir) + 1) % len(DIRS)]
                 g[pos] = DIRCHAR[DIRS.index(dir)]
-        g.print()
-        input()
-        print()
+
+        # For debugging:
+        # g.print()
+        # input()
+        # print()
     path = path.replace("RRR", "L")
     return path
 
@@ -81,14 +83,48 @@ def part_1(data):
                 # g[(r, c)] = 'o'
                 result += r * c
     print(result)
-    g.print()
-    path = find_path(g)
-    print(path)
+    # g.print()
 
-    # xs = str_to_ints(data)
-    # xs[0] = 2
-    # a = Amp(xs)
-    # a.go()
+    # 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():

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/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)

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/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/d4.py

@@ -1,4 +1,4 @@
-from lib import get_data, Grid2D
+from lib import get_data
 
 required = [
     "byr",
@@ -7,7 +7,8 @@ required = [
     "hgt",
     "hcl",
     "ecl",
-    "pid",]
+    "pid",
+]
 
 
 # hgt (Height) - a number followed by either cm or in:

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()

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)

2021/d20.py

@@ -0,0 +1,51 @@
+from lib import get_data
+
+data = get_data(__file__)
+
+for rounds in [2, 50]:
+    algo, img = data.strip().split("\n\n")
+    algo = algo.replace("\n", "")
+
+    xs = set()
+    img = img.splitlines()
+    for row in range(len(img)):
+        for col in range(len(img[0])):
+            if img[row][col] == "#":
+                xs.add((row, col))
+
+    for i in range(rounds):
+        y_min = min(v[0] for v in xs) - 6
+        y_max = max(v[0] for v in xs) + 6
+        x_min = min(v[1] for v in xs) - 6
+        x_max = max(v[1] for v in xs) + 6
+
+        nxs = set()
+        for row in range(y_min, y_max + 1):
+            for col in range(x_min, x_max + 1):
+                bin = ""
+                for ro in range(3):
+                    for co in range(3):
+                        if (row + ro, col + co) in xs:
+                            bin += "1"
+                        else:
+                            bin += "0"
+                bin = int(bin, 2)
+                if algo[bin] == "#":
+                    nxs.add((row, col))
+
+        xs = nxs
+        y_min_trim = y_min + 7
+        y_max_trim = y_max - 8
+        x_min_trim = x_min + 7
+        x_max_trim = x_max - 8
+
+        # special clean-up required because input creates pixels when there
+        # are no other pixels around (0b0_0000_0000)
+        if i % 2 == 1:
+            xs = [
+                (r, c)
+                for (r, c) in xs
+                if y_min_trim <= r <= y_max_trim and x_min_trim <= c <= x_max_trim
+            ]
+
+    print(len(xs))

2021/d21.py

@@ -0,0 +1,65 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+
+FIELD = 10
+DICE = 100
+dice = -1
+
+data = get_data(__file__)
+
+_, p1, _, p2 = ints(data)
+pos = [p1 - 1, p2 - 1]
+scores = [0, 0]
+
+dice_rolls = 0
+not_done = True
+while not_done:
+    for p in range(len(scores)):
+        dice_rolls += 3
+        for _ in range(3):
+            dice += 1 % DICE
+            pos[p] = (pos[p] + (dice + 1)) % FIELD
+        scores[p] += pos[p] + 1
+        if scores[p] >= 1000:
+            not_done = False
+            break
+
+r = min(scores) * dice_rolls
+print(r)
+
+_, p1, _, p2 = ints(data)
+pos = (p1 - 1, p2 - 1)
+scores = (0, 0)
+unis = defaultdict(int)
+won = [0, 0]
+unis[(0, pos, scores)] += 1
+
+while unis:
+    nunis = defaultdict(int)
+    for (turn, opos, scores), count in unis.items():
+        other = (turn + 1) % 2
+        poss = [opos[turn]]
+        for _ in range(3):
+            nposs = []
+            for dice in range(1, 3 + 1):
+                for pos in poss:
+                    npos = (pos + dice) % FIELD
+                    nposs.append(npos)
+            poss = nposs
+
+        for npos_player in poss:
+            score = scores[turn] + npos_player + 1
+            if score >= 21:
+                won[turn] += count
+            else:
+                nscores = list(scores)
+                nscores[turn] = score
+                npos = list(opos)
+                npos[turn] = npos_player
+                state = (other, tuple(npos), tuple(nscores))
+                nunis[state] += count
+    unis = nunis
+
+print(max(won))

2021/d22.py

@@ -0,0 +1,92 @@
+from lib import get_data
+from lib import ints
+from dataclasses import dataclass
+from typing import Optional
+
+data = get_data(__file__)
+
+limit = 50
+ps = set()
+for i, line in enumerate(data.splitlines()):
+    x_min, x_max, y_min, y_max, z_min, z_max = ints(line)
+    for x in range(max(x_min, -limit), min(x_max, limit) + 1):
+        for y in range(max(y_min, -limit), min(y_max, limit) + 1):
+            for z in range(max(z_min, -limit), min(z_max, limit) + 1):
+                if line.startswith("on"):
+                    ps.add((x, y, z))
+                elif line.startswith("off"):
+                    if (x, y, z) in ps:
+                        ps.remove((x, y, z))
+                else:
+                    assert False
+
+print(len(ps))
+
+
+@dataclass
+class Line:
+    a: int
+    b: int
+
+    def intersects(self, other: "Line") -> bool:
+        return self.b > other.a and self.a < other.b
+
+    def intersection(self, other: "Line") -> Optional["Line"]:
+        if not self.intersects(other):
+            return None
+        return Line(max(self.a, other.a), min(self.b, other.b))
+
+    def length(self) -> int:
+        assert self.b > self.a
+        return self.b - self.a + 1
+
+
+@dataclass(frozen=True)
+class Cube:
+    on: bool
+    x: Line
+    y: Line
+    z: Line
+
+    @classmethod
+    def from_line(cls, line: str) -> "Cube":
+        xs = ints(line)
+        assert len(xs) == 6
+        lines = [Line(*xs[i:i+2]) for i in range(0, len(xs), 2)]
+        on = True if line.startswith("on") else False
+        return Cube(on, *lines)
+
+    def volume(self) -> int:
+        return (self.x.length() * self.y.length() * self.z.length()) * (1 if self.on else -1)
+
+    def intersects(self, other: "Cube") -> bool:
+        return (
+            self.x.intersects(other.x)
+            and self.y.intersects(other.y)
+            and self.z.intersects(other.z)
+        )
+
+    def intersection(self, other: "Cube") -> Optional["Cube"]:
+        x = self.x.intersection(other.x)
+        y = self.y.intersection(other.y)
+        z = self.z.intersection(other.z)
+        if x is None or y is None or z is None:
+            return None
+        return Cube(not self.on, x, y, z)
+
+
+# Inclusion/exclusion principle from set theory
+cubes = []
+for line in data.splitlines():
+    cc = Cube.from_line(line)
+    ncubes = []
+    for i in range(len(cubes)):
+        c = cubes[i]
+        ic = c.intersection(cc)
+        if ic is not None:
+            cubes.append(ic)
+
+    if cc.on:
+        cubes.append(cc)
+
+print(sum(c.volume() for c in cubes))

2021/d23.py

@@ -0,0 +1,143 @@
+import heapq
+from lib import get_data
+from lib import Grid2D
+from collections import deque
+from collections import defaultdict
+
+CHAR_COSTS = {"A": 1, "B": 10, "C": 100, "D": 1000}
+HALL_SPOTS = set([(1, x) for x in [1, 2, 4, 6, 8, 10, 11]])
+
+for n_amphs in [2, 4]:
+    AMPH_SPOTS = {}
+    for i, c in enumerate("ABCD"):
+        spots = [(r, 3 + i * 2) for r in range(2, 2 + n_amphs)]
+        AMPH_SPOTS[c] = tuple(spots)
+
+    data = get_data(__file__)
+    lines = data.splitlines()
+    if n_amphs == 4:
+        lines.insert(-2, "  #D#C#B#A#  ")
+        lines.insert(-2, "  #D#B#A#C#  ")
+    lines[-2] = lines[-2] + "  "
+    lines[-1] = lines[-1] + "  "
+    data = "\n".join(lines)
+
+    g = Grid2D(data)
+    GRID_EMPTY = g.clone()
+
+    def mdist(p1, p2):
+        return abs(p1[0] - p2[0]) + abs(p1[1] - p2[1])
+
+    poss = []
+    for c in "ABCD":
+        for coord in g.find(c):
+            poss.append((coord[0], coord[1], c, False))
+            GRID_EMPTY[coord] = "."
+    poss = tuple(poss)
+
+    def dist(n1, n2):
+        """cost from node to node"""
+        if n1 == 0:
+            return 0
+        return n2[1] - n1[1]
+
+    def h(node):
+        """heuristic function (never overestimate)"""
+        cost = 0
+        for r, c, char, _ in node[0]:
+            if (r, c) not in AMPH_SPOTS[char]:
+                cost += mdist((r, c), AMPH_SPOTS[char][0]) * CHAR_COSTS[char]
+        return cost
+
+    def is_goal(node):
+        for r, c, char, _ in node[0]:
+            if (r, c) in AMPH_SPOTS[char]:
+                continue
+            return False
+        return True
+
+    def find_accessible_spots(pos: tuple[int, int], char, blocked):
+        start = (pos, 0)
+        visited = set()
+        queue = deque([start])
+        cost = CHAR_COSTS[char]
+
+        options = []
+        while queue:
+            pos, dist = queue.popleft()
+            if pos in visited:
+                continue
+            visited.add(pos)
+
+            for neighbor in GRID_EMPTY.neighbors_ort(pos):
+                if neighbor in blocked:
+                    continue
+                if GRID_EMPTY[neighbor] != ".":
+                    continue
+                if neighbor not in visited:
+                    new_state = (neighbor, dist + cost)
+                    queue.append(new_state)
+                    options.append(new_state)
+        return options
+
+    def neighbors(node):
+        nbs = []
+
+        blocked = []
+        blocked_to_char = defaultdict(str)
+        for r, c, char, _ in node[0]:
+            blocked.append((r, c))
+            blocked_to_char[(r, c)] = char
+
+        for i, (r, c, char, moved) in enumerate(node[0]):
+            if moved and (r, c) in AMPH_SPOTS[char]:
+                continue
+
+            for pos, dist in find_accessible_spots((r, c), char, blocked):
+                # cannot move to hall spots twice
+                if pos in HALL_SPOTS and moved:
+                    continue
+
+                # can only move to hall spot or amph spot (of the right type)
+                if not (pos in HALL_SPOTS or pos in AMPH_SPOTS[char]):
+                    continue
+
+                # only move into amph spot if all lower spots are already occupied by the correct amph
+                if pos in AMPH_SPOTS[char] and not all(
+                    blocked_to_char[AMPH_SPOTS[char][i]] == char
+                    for i in range(
+                        AMPH_SPOTS[char].index(pos) + 1, len(AMPH_SPOTS[char])
+                    )
+                ):
+                    continue
+
+                amphs = list(node[0])
+                amphs[i] = (pos[0], pos[1], char, True)
+                neighbor = (tuple(amphs), node[1] + dist)
+                nbs.append(neighbor)
+        return nbs
+
+    starts = [(poss, 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/d24.py

@@ -0,0 +1,45 @@
+from lib import get_data
+
+data = get_data(__file__)
+
+
+def run(number):
+    inputs = list(map(int, str(number)))
+    assert len(inputs) == 14
+
+    w, x, z = 0, 0, 0
+    i = 0
+    for i in range(len(inputs)):
+        w = inputs[i]
+        # print(f"{w=:3} {x=:3}                       {z=}")
+
+        to_add_x = [15, 15, 12, 13, -12, 10, -9, 14, 13, -14, -11, -2, -16, -14][i]
+        to_div_z = [1, 1, 1, 1, 26, 1, 26, 1, 1, 26, 26, 26, 26, 26][i]
+        to_add_z = [15, 10, 2, 16, 12, 11, 5, 16, 6, 15, 3, 12, 10, 13][i]
+
+        zz = z
+        x = (z % 26) + to_add_x
+        z = z // to_div_z
+
+        # print(f"{zz % 26=} + {to_add_x=} {x=}")
+
+        if x == w:
+            # print(f"added                     = 0")
+            pass
+        else:
+            z *= 26
+            z += w + to_add_z
+            # print(f"added {w=} + {to_add_z=} = {w + to_add_z}")
+        # print()
+
+    # print(f"\nEND:\n{w=} {x=} {z=}", "\n" * 15)
+    return z
+
+
+largest_model_nr = 89959794919939
+assert run(largest_model_nr) == 0
+print(largest_model_nr)
+
+lowest_model_nr = 17115131916112
+assert run(lowest_model_nr) == 0
+print(lowest_model_nr)

2021/d25.py

@@ -0,0 +1,29 @@
+from lib import get_data
+from lib import Grid2D
+
+data = get_data(__file__)
+
+g = Grid2D(data)
+seen = set()
+for i in range(10**9):
+    if g.hash() in seen:
+        print(i)
+        break
+
+    seen.add(g.hash())
+    blocked = set(g.find(">v"))
+    for p in g.find(">"):
+        np = (p[0], (p[1] + 1) % g.n_cols)
+        if np in blocked:
+            continue
+        g[p] = "."
+        g[np] = ">"
+
+    blocked = set(g.find(">v"))
+    for p in g.find("v"):
+        np = ((p[0] + 1) % g.n_rows , p[1])
+        if np in blocked:
+            continue
+        g[p] = "."
+        g[np] = "v"
+

2021/d3.py

@@ -0,0 +1,56 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+data = get_data(__file__)
+
+
+def count_one_zero(xs, index):
+    ones, zeros = 0, 0
+    for x in xs:
+        if x[index] == "1":
+            ones += 1
+        elif x[index] == "0":
+            zeros += 1
+        else:
+            assert False
+    return (ones, zeros)
+
+
+a = ""
+b = ""
+lines = list(data.strip().splitlines())
+for i in range(len(lines[0])):
+    ones, zeros = count_one_zero(lines, i)
+    if ones > zeros:
+        a += "1"
+        b += "0"
+    elif zeros > ones:
+        a += "0"
+        b += "1"
+    else:
+        assert False
+a, b = int(a, 2), int(b, 2)
+print(a * b)
+
+lines = list(data.strip().splitlines())
+for i in range(len(lines[0])):
+    ones, zeros = count_one_zero(lines, i)
+    c = "1" if ones >= zeros else "0"
+    lines = [l for l in lines if l[i] == c]
+    if len(lines) == 1:
+        break
+(line,) = lines
+a = int(line, 2)
+
+lines = list(data.strip().splitlines())
+for i in range(len(lines[0])):
+    ones, zeros = count_one_zero(lines, i)
+    c = "0" if zeros <= ones else "1"
+    lines = [l for l in lines if l[i] == c]
+    if len(lines) == 1:
+        break
+
+(line,) = lines
+b = int(line, 2)
+print(a * b)

2021/d4.py

@@ -0,0 +1,52 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__).strip()
+
+boards = []
+numbers = None
+for i, p in enumerate(data.split("\n\n")):
+    if i == 0:
+        numbers = ints(p)
+    else:
+        board = []
+        for line in p.splitlines():
+            board.append(ints(line))
+        boards.append(board)
+
+assert numbers is not None
+first_won = None
+last_won = None
+boards_done = list()
+for n in numbers:
+    for i in range(len(boards)):
+        if i in boards_done:
+            continue
+        board = boards[i]
+        board = [[f if n != f else None for f in row] for row in board]
+        boards[i] = board
+        for row in board:
+            if all(cell is None for cell in row):
+                if not i in boards_done:
+                    boards_done.append(i)
+        for col in zip(*board):
+            if all(cell is None for cell in col):
+                if not i in boards_done:
+                    boards_done.append(i)
+
+        if len(boards_done) > 0 and first_won is None:
+            first_won = (i, n)
+
+        if len(boards_done) == len(boards):
+            last_won = (i, n)
+            break
+    if len(boards_done) == len(boards):
+        break
+
+assert first_won is not None
+assert last_won is not None
+
+for i, n in [first_won, last_won]:
+    board = boards[i]
+    a = sum([sum([n if n is not None else 0 for n in row]) for row in board])
+    print(a * n)

2021/d5.py

@@ -0,0 +1,39 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+data = get_data(__file__).strip()
+
+counts = defaultdict(int)
+for line in data.splitlines():
+    x1, y1, x2, y2 = ints(line)
+    if x1 == x2 or y1 == y2:
+        if x1 == x2:
+            for y in range(min(y1, y2), max(y1, y2) + 1):
+                counts[(x1, y)] += 1
+        elif y1 == y2:
+            for x in range(min(x1, x2), max(x1, x2) + 1):
+                counts[(x, y1)] += 1
+        else:
+            assert False
+
+r = sum(1 for v in counts.values() if v > 1)
+print(r)
+
+
+for line in data.splitlines():
+    x1, y1, x2, y2 = ints(line)
+    if x1 == x2 or y1 == y2:
+        pass
+    else:
+        dx = 1 if x2 > x1 else -1
+        dy = 1 if y2 > y1 else -1
+
+        while (x1, y1) != (x2, y2):
+            counts[(x1, y1)] += 1
+            x1 += dx
+            y1 += dy
+        counts[(x2, y2)] += 1
+
+r = sum(1 for v in counts.values() if v > 1)
+print(r)

2021/d6.py

@@ -0,0 +1,32 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+data = get_data(__file__).strip()
+xs = ints(data)
+
+for _ in range(80):
+    for i in range(len(xs)):
+        if xs[i] == 0:
+            xs[i] = 6
+            xs.append(8)
+        else:
+            xs[i] -= 1
+
+print(len(xs))
+
+xs = ints(data)
+fish = defaultdict(int)
+for x in xs:
+    fish[x] += 1
+
+for _ in range(256):
+    new_fish = defaultdict(int)
+    new_fish[8] = fish[0]
+    new_fish[6] = fish[0]
+    for i in range(1, 9):
+        new_fish[i - 1] += fish[i]
+    fish = new_fish
+
+r = sum(fish.values())
+print(r)

2021/d7.py

@@ -0,0 +1,20 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__).strip()
+xs = ints(data)
+
+
+def d(t, x):
+    n = abs(t - x)
+    return n * (n + 1) // 2
+
+
+s_min_1 = 10**16
+s_min_2 = 10**16
+for t in range(min(xs), max(xs) + 1):
+    s_min_1 = min(s_min_1, sum(abs(t - x) for x in xs))
+    s_min_2 = min(s_min_2, sum(d(t, x) for x in xs))
+
+print(s_min_1)
+print(s_min_2)

2021/d8.py

@@ -0,0 +1,65 @@
+from lib import get_data
+from itertools import permutations
+
+data = get_data(__file__).strip()
+
+code_to_num = {
+    "cf": 1,
+    "acf": 7,
+    "bcdf": 4,
+    "acdeg": 2,
+    "acdfg": 3,
+    "abdfg": 5,
+    "abcefg": 0,
+    "abdefg": 6,
+    "abcdfg": 9,
+    "abcdefg": 8,
+}
+
+
+def translate(inn, mapping):
+    out = ""
+    for c in inn:
+        out += mapping[c]
+    return "".join(sorted(out))
+
+
+def decode(inn, out):
+    s = "abcdefg"
+    m = None
+    for p in permutations(s):
+        m = {k: v for k, v in zip(p, s)}
+        all = set(code_to_num.keys())
+        for in_code in inn:
+            out_code = translate(in_code, m)
+            if out_code in all:
+                all.remove(out_code)
+
+        if len(all) == 0:
+            break
+        else:
+            m = None
+
+    assert m is not None
+
+    o = 0
+    d = 1000
+    for out_code in out:
+        out_code = translate(out_code, m)
+        v = code_to_num[out_code]
+        o += d * v
+        d //= 10
+    return o
+
+
+s1 = 0
+s2 = 0
+for line in data.splitlines():
+    inn, out = line.strip().split(" | ")
+    inn = inn.split()
+    out = out.split()
+    s1 += sum(1 for v in out if len(v) in [2, 3, 4, 7])
+    s2 += decode(inn, out)
+
+print(s1)
+print(s2)

2021/d9.py

@@ -0,0 +1,47 @@
+from lib import get_data, Grid2D
+from collections import deque
+
+data = get_data(__file__).strip()
+g = Grid2D(data)
+
+s = 0
+low_points = []
+for row in range(g.n_rows):
+    for col in range(g.n_cols):
+        h = int(g[(row, col)])
+        for nb in g.neighbors_ort((row, col)):
+            if int(g[nb]) <= h:
+                break
+        else:
+            low_points.append((row, col))
+            s += 1 + h
+
+print(s)
+
+basins = []
+for row, col in low_points:
+    start = None
+    visited = set()
+    queue = deque([(row, col)])
+
+    while queue:
+        vertex = queue.popleft()
+        if vertex in visited:
+            continue
+        visited.add(vertex)
+
+        neighbors = []
+        for neighbor in g.neighbors_ort(vertex):
+            if neighbor in visited:
+                continue
+
+            neighbor_height = int(g[neighbor])
+            if neighbor_height < 9:
+                queue.append(neighbor)
+
+    basins.append(len(visited))
+
+s = 1
+for x in sorted(basins)[-3:]:
+    s *= x
+print(s)

2021/lib.py

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

2022/d19.py

@@ -1,117 +1,66 @@
-from lib import *
+import re
+from lib import get_data, str_to_ints
+from math import ceil
 
-EXAMPLE = """
-Blueprint 1:
-  Each ore robot costs 4 ore.
-  Each clay robot costs 2 ore.
-  Each obsidian robot costs 3 ore and 14 clay.
-  Each geode robot costs 2 ore and 7 obsidian.
+data = get_data(__file__)
 
-Blueprint 2:
-  Each ore robot costs 2 ore.
-  Each clay robot costs 3 ore.
-  Each obsidian robot costs 3 ore and 8 clay.
-  Each geode robot costs 3 ore and 12 obsidian.
-"""
+p1 = 0
+p2 = 1
 
-def solve(input: Input, second=False):
-    if not second:
-        res = 0
-    else:
-        res = 1
+for line in data.splitlines():
+    id = str_to_ints(line)[0]
     bps = []
-    for line in input.text.replace(".", ".\n").replace(":", ":\n").splitlines():
-        if "Blueprint" in line:
-            bps.append([])
-        elif "ore robot" in line:
-            cost = str_to_ints(line)
-            cost += [0, 0]
-            bps[-1].append(cost)
-        elif "clay robot" in line:
-            cost = str_to_ints(line)
-            cost += [0, 0]
-            bps[-1].append(cost)
-        elif "obsidian robot" in line:
-            cost = str_to_ints(line)
-            cost += [0,]
-            bps[-1].append(cost)
-        elif "geode robot" in line:
-            cost = str_to_ints(line)
-            cost.insert(1, 0)
-            bps[-1].append(cost)
+    maxmin = [0, 0, 0]
+    for part in line.split(". "):
+        bp = []
+        for amount, mineral in re.findall(r"(\d+) (\w+)", part):
+            amount = int(amount)
+            mi = ["ore", "clay", "obsidian", "geode"].index(mineral)
+            bp.append((amount, mi))
+            maxmin[mi] = max(maxmin[mi], amount)
+        bps.append(bp)
 
-    if second:
-        bps = bps[:3]
-        time = 32
-    else:
-        time = 24
+    def dfs(time, mins, bots, cache):
+        if time == 0:
+            return mins[3]
 
-    end_states = []
-    for i, bp in enumerate(bps):
-        # ((ore bots, clay bots, obs bots, geo bots), (ore, clay, obs, geo))
-        start = ((1, 0, 0, 0), (0, 0, 0, 0))
-        states = [start]
-        seen = set(states)
+        key = (time, *mins, *bots)
+        if key in cache:
+            return cache[key]
 
-        for _ in range(time):
-            new_states = []
-            while states:
-                bots, ress = states.pop()
+        maxv = mins[3] + time * bots[3]
+        for bi, recipe in enumerate(bps):
+            if bi != 3 and bots[bi] >= maxmin[bi]:
+                continue
 
-                add_ress = [0, 0, 0, 0]
-                for boti, count in enumerate(bots):
-                    add_ress[boti] += count
+            wait = 0
+            for ra, ri in recipe:
+                if bots[ri] == 0:
+                    break
+                wait = max(ceil((ra - mins[ri]) / bots[ri]), wait)
+            else:
+                remtime = time - wait - 1
+                if remtime <= 0:
+                    continue
 
-                all_built = True
-                for boti, cost in enumerate(bp):
-                    if ress[0] >= cost[0] and ress[1] >= cost[1] and ress[2] >= cost[2]:
-                        new_ress = list(ress)
-                        new_ress[0] -= cost[0]
-                        new_ress[1] -= cost[1]
-                        new_ress[2] -= cost[2]
-                        new_ress = tuple(map(sum, zip(new_ress, add_ress)))
-                        new_bots = list(bots)
-                        new_bots[boti] += 1
-                        new_state = (tuple(new_bots), new_ress)
-                        if not new_state in seen:
-                            new_states.append(new_state)
-                            seen.add(new_state)
-                    else:
-                        all_built = False
+                bots_ = list(bots)
+                mins_ = [m + b * (wait + 1) for m, b in zip(mins, bots)]
+                for ra, ri in recipe:
+                    mins_[ri] -= ra
+                bots_[bi] += 1
 
-                # XXX: our search space is too large here it is possible to
-                # optimze by not storing reduntant paths (paths where we acrue
-                # more of a resource than we need), but I don't know how to
-                # make it more efficient right now.
-                if not all_built:
-                    new_ress = tuple(map(sum, zip(ress, add_ress)))
-                    new_state = (bots, new_ress)
-                    if not new_state in seen:
-                        new_states.append(new_state)
-                        seen.add(new_state)
+                for i in range(3):
+                    mins_[i] = min(mins_[i], maxmin[i] * remtime)
+                v = dfs(remtime, tuple(mins_), tuple(bots_), cache)
+                maxv = max(v, maxv)
 
-            # prune to keep search space "reasonable"
-            states = sorted(new_states, key=lambda s: list(reversed(s[0])), reverse=True)[:100000]
+        key = (time, *mins, *bots)
+        cache[key] = maxv
+        return maxv
 
-        if not second:
-            r = max(states, key=lambda s: s[1][3])
-            q = (i + 1) * r[1][3]
-            # print(i + 1, r, q)
-            res += q
-        else:
-            r = max(states, key=lambda r: r[1][3])
-            res *= r[1][3]
-    return res
+    p1 += id * dfs(24, (0, 0, 0, 0), (1, 0, 0, 0), {})
+    if id < 4:
+        p2 *= dfs(32, (0, 0, 0, 0), (1, 0, 0, 0), {})
 
-def main():
-    DAY_INPUT = "d19.txt"
-    e1 = solve(Input(EXAMPLE))
-    print("Example  1:", e1)
-    assert e1 == 33
-    print("Solution 1:", solve(Input(DAY_INPUT)))
-    print("Example  2:", solve(Input(EXAMPLE), True))
-    print("Solution 2:", solve(Input(DAY_INPUT), True))
-    return
-
-if __name__ == "__main__":
-    main()
+print(p1)
+print(p2)

2024/d01.py

@@ -0,0 +1,21 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__)
+
+s = 0
+ass, bss = [], []
+s2 = 0
+
+# I had an intuition for this and then went for loops...
+xs, ys = list(zip(*[ints(line) for line in data.splitlines()]))
+
+xs = sorted(xs)
+ys = sorted(ys)
+
+for a, b in zip(xs, ys):
+    s += max(a, b) - min(a, b)
+    s2 += ys.count(a) * a
+
+print(s)
+print(s2)

2024/d02.py

@@ -0,0 +1,42 @@
+from lib import get_data
+from lib import ints
+
+
+data = get_data(__file__)
+
+s1 = 0
+s2 = 0
+
+for line in data.splitlines():
+    xs = ints(line)
+
+    deltas = []
+    for i in range(len(xs) - 1):
+        deltas.append(xs[i + 1] - xs[i])
+        if abs(xs[i + 1] - xs[i]) not in [1, 2, 3]:
+            break
+    else:
+        if deltas[0] < 0 and all(deltas[i] < 0 for i in range(len(deltas))):
+            s1 += 1
+        elif deltas[0] > 0 and all(deltas[i] > 0 for i in range(len(deltas))):
+            s1 += 1
+
+    sublists = [xs[:i] + xs[i + 1 :] for i in range(len(xs))]
+    found = False
+    for xs in sublists:
+        deltas = []
+        for i in range(len(xs) - 1):
+            deltas.append(xs[i + 1] - xs[i])
+            if abs(xs[i + 1] - xs[i]) not in [1, 2, 3]:
+                break
+        else:
+            if deltas[0] < 0 and all(deltas[i] < 0 for i in range(len(deltas))):
+
+                found = True
+            if deltas[0] > 0 and all(deltas[i] > 0 for i in range(len(deltas))):
+                found = True
+    if found:
+        s2 += 1
+
+print(s1)
+print(s2)

2024/d03.py

@@ -0,0 +1,24 @@
+import re
+from lib import get_data
+from lib import ints
+
+
+data = get_data(__file__)
+
+t1 = 0
+t2 = 0
+enabled = True
+r = re.compile(r"mul\(\d+,\d+\)|do\(\)|don't\(\)")
+for m in r.findall(data):
+    if m == "do()":
+        enabled = True
+    elif m == "don't()":
+        enabled = False
+    else:
+        a, b = ints(m)
+        t1 += a * b
+        if enabled:
+            t2 += a * b
+
+print(t1)
+print(t2)

2024/d04.py

@@ -0,0 +1,44 @@
+from lib import get_data
+from lib import Grid2D
+
+data = get_data(__file__)
+g = Grid2D(data)
+
+DIRS = {
+    "N": (-1, 0),
+    "E": (0, 1),
+    "S": (1, 0),
+    "W": (0, -1),
+    "NE": (-1, 1),
+    "SE": (1, 1),
+    "SW": (1, -1),
+    "NW": (-1, -1),
+}
+
+t1, t2 = 0, 0
+for row in range(g.n_rows):
+    for col in range(g.n_cols):
+        for d in DIRS.values():
+            coords = [(row + d[0] * i, col + d[1] * i) for i in range(len("XMAS"))]
+            for (r, c), z in zip(coords, "XMAS"):
+                if not (0 <= r < g.n_rows and 0 <= c < g.n_cols and g[(r, c)] == z):
+                    break
+            else:
+                t1 += 1
+
+        coords = [
+            (row - 1, col - 1),
+            (row - 1, col + 1),
+            (row, col),
+            (row + 1, col - 1),
+            (row + 1, col + 1),
+        ]
+        for s in ["MMASS", "MSAMS", "SSAMM", "SMASM"]:
+            for (r, c), z in zip(coords, s):
+                if not (0 <= r < g.n_rows and 0 <= c < g.n_cols and g[(r, c)] == z):
+                    break
+            else:
+                t2 += 1
+
+print(t1)
+print(t2)

2024/d05.py

@@ -0,0 +1,37 @@
+from lib import get_data
+from lib import ints
+
+
+def fix(xs):
+    change = True
+    while change:
+        change = False
+        for rule in rules.splitlines():
+            x, y = ints(rule)
+            if not (x in xs and y in xs):
+                continue
+            i, j = xs.index(x), xs.index(y)
+            if not i < j:
+                xs[i], xs[j] = xs[j], xs[i]
+                change = True
+    return xs
+
+
+rules, pages = get_data(__file__).split("\n\n")
+
+t1, t2 = 0, 0
+for page in pages.splitlines():
+    xs = ints(page)
+    for rule in rules.splitlines():
+        x, y = ints(rule)
+        if not (x in xs and y in xs):
+            continue
+        if not (xs.index(x) < xs.index(y)):
+            xs = fix(ints(page))
+            t2 += xs[len(xs) // 2]
+            break
+    else:
+        t1 += xs[len(xs) // 2]
+
+print(t1)
+print(t2)

2024/d06.py

@@ -0,0 +1,51 @@
+from lib import get_data
+from lib import Grid2D
+
+data = get_data(__file__)
+
+
+DIRS = [
+    (-1, 0),
+    (0, 1),
+    (1, 0),
+    (0, -1),
+]
+
+g = Grid2D(data)
+
+t = 0
+for rr in range(g.n_rows):
+    for cc in range(g.n_cols):
+        (p,), dir = g.find("^"), 0
+        seen = set()
+        loop = False
+
+        if g[(rr, cc)] == "#":
+            continue
+
+        if g[(rr, cc)] != "^":
+            g[(rr, cc)] = "#"
+
+        while True:
+            if (p, dir) in seen:
+                loop = True
+                break
+            seen.add((p, dir))
+            r, c = p[0] + DIRS[dir][0], p[1] + DIRS[dir][1]
+            if not (0 <= r < g.n_rows and 0 <= c < g.n_cols):
+                break
+
+            if g[(r, c)] == "#":
+                dir = (dir + 1) % 4
+            else:
+                p = (r, c)
+
+        if g[(rr, cc)] == "^":
+            print(len(set(pos for pos, _ in seen)))
+        else:
+            g[(rr, cc)] = "."
+
+        if loop:
+            t += 1
+
+print(t)

2024/d07.py

@@ -0,0 +1,30 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__)
+
+
+def combs(acc, rest, part_2=False):
+    if rest == []:
+        return acc
+
+    nacc = []
+    for a in acc:
+        nacc.append(a + rest[0])
+        nacc.append(a * rest[0])
+        if part_2:
+            nacc.append(int(str(a) + str(rest[0])))
+    return combs(nacc, rest[1:], part_2)
+
+
+t1, t2 = 0, 0
+for line in data.splitlines():
+    xs = ints(line)
+    expected = xs[0]
+    if xs[0] in combs([xs[1]], xs[2:]):
+        t1 += xs[0]
+    if xs[0] in combs([xs[1]], xs[2:], True):
+        t2 += xs[0]
+
+print(t1)
+print(t2)

2024/d08.py

@@ -0,0 +1,34 @@
+from lib import get_data
+from lib import Grid2D
+from itertools import combinations
+from collections import defaultdict
+
+data = get_data(__file__)
+g = Grid2D(data)
+
+d = defaultdict(list)
+
+for row in range(g.n_rows):
+    for col in range(g.n_cols):
+        p = (row, col)
+        if g[p] != ".":
+            d[g[p]].append((row, col))
+
+aa = set()
+bb = set()
+for coords in d.values():
+    for c, d in combinations(coords, 2):
+        bb.add(c)
+        bb.add(d)
+        for a, b in [(c, d), (d, c)]:
+            d = b[0] - a[0], b[1] - a[1]
+            a = b[0] + d[0], b[1] + d[1]
+            if g.contains(a):
+                aa.add(a)
+            a = b[0] + d[0], b[1] + d[1]
+            while g.contains(a):
+                bb.add(a)
+                a = a[0] + d[0], a[1] + d[1]
+
+print(len(aa))
+print(len(bb))

2024/d09.py

@@ -0,0 +1,102 @@
+from lib import get_data
+from copy import deepcopy
+
+data = get_data(__file__)
+i = 0
+f = True
+d = []
+spaces = 0
+for c in data.strip():
+    if f:
+        d.append([int(c), i, f])
+        f = False
+        i += 1
+    else:
+        spaces += int(c)
+        d.append([int(c), -1, f])
+        f = True
+
+d2 = deepcopy(d)
+
+BLOCKS, ID, FULL = 0, 1, 2
+empty_i = 1
+full_i = len(d) - 1
+assert d[full_i][FULL]
+
+while empty_i < full_i:
+    empty = d[empty_i]
+    full = d[full_i]
+
+    if empty[BLOCKS] == full[BLOCKS]:
+        empty[ID] = full[ID]
+        empty[FULL] = True
+        full[BLOCKS] = 0
+        full[FULL] = False
+    elif empty[BLOCKS] < full[BLOCKS]:
+        empty[ID] = full[ID]
+        empty[FULL] = True
+        full[BLOCKS] -= empty[BLOCKS]
+    elif empty[BLOCKS] > full[BLOCKS]:
+        new = [empty[BLOCKS] - full[BLOCKS], empty[ID], False]
+        empty[ID] = full[ID]
+        empty[BLOCKS] = full[BLOCKS]
+        empty[FULL] = True
+        d.insert(empty_i + 1, new)
+        full_i += 1
+        full[BLOCKS] = 0
+        full[FULL] = False
+    else:
+        assert False
+
+    while d[empty_i][FULL] == True:
+        empty_i += 1
+
+    while d[full_i][FULL] == False:
+        full_i -= 1
+
+t = 0
+i = 0
+for b in d:
+    if b[FULL] == False:
+        break
+    for _ in range(b[BLOCKS]):
+        t += i * b[ID]
+        i += 1
+print(t)
+
+d = d2
+
+full_i = len(d) - 1
+while full_i > 0:
+    full = d[full_i]
+    prev_i = full_i
+    for empty_i in range(0, full_i):
+        empty = d[empty_i]
+        if full[FULL] == False:
+            continue
+        if empty[FULL]:
+            continue
+        if empty[BLOCKS] < full[BLOCKS]:
+            continue
+
+        if empty[BLOCKS] == full[BLOCKS]:
+            empty[FULL] = True
+            empty[ID] = full[ID]
+            full[FULL] = False
+        elif empty[BLOCKS] > full[BLOCKS]:
+            full[FULL] = False
+            new = [full[BLOCKS], full[ID], True]
+            d[empty_i] = new
+            d.insert(empty_i + 1, [empty[BLOCKS] - full[BLOCKS], -1, False])
+            full_i += 1
+        break
+    full_i -= 1
+
+t = 0
+i = 0
+for b in d:
+    for _ in range(b[BLOCKS]):
+        if b[FULL] == True:
+            t += i * b[ID]
+        i += 1
+print(t)

2024/d09_2.py

@@ -0,0 +1,81 @@
+from lib import get_data
+
+data = get_data("d9.py")
+
+
+def parse(data):
+    xs = []
+    f = True
+    i = 0
+    for c in data.strip():
+        if f:
+            for _ in range(int(c)):
+                xs.append(i)
+            f = False
+            i += 1
+        else:
+            for _ in range(int(c)):
+                xs.append(".")
+            f = True
+    return xs
+
+
+def score(xs):
+    t = 0
+    for i, j in enumerate(xs):
+        if j == ".":
+            continue
+        t += i * j
+    return t
+
+
+xs = parse(data)
+i, j = 0, len(xs) - 1
+while i <= j:
+    while xs[i] != ".":
+        i += 1
+
+    while xs[j] == ".":
+        j -= 1
+
+    if not i <= j:
+        break
+
+    xs[i], xs[j] = xs[j], xs[i]
+
+print(score(xs))
+xs = parse(data)
+
+idx = {}
+ids = []
+for i, x in enumerate(xs):
+    if x == ".":
+        continue
+    if not x in idx:
+        idx[x] = i
+        ids.append(x)
+
+while ids:
+    id = ids.pop()
+    i1, i2 = idx[id], idx[id]
+    while i2 < len(xs) and xs[i2] == id:
+        i2 += 1
+
+    j1 = 0
+    while j1 < i1:
+        while xs[j1] != ".":
+            j1 += 1
+        if not j1 < i1:
+            break
+        j2 = j1
+        while xs[j2] == ".":
+            j2 += 1
+        assert j2 <= i1
+
+        if i2 - i1 <= j2 - j1:
+            for j, i in zip(range(j1, j2), range(i1, i2)):
+                xs[j], xs[i] = xs[i], xs[j]
+            break
+        j1 = j2
+
+print(score(xs))

2024/d10.py

@@ -0,0 +1,26 @@
+from collections import deque
+from lib import Grid2D
+from lib import get_data
+
+
+data = get_data(__file__)
+g = Grid2D(data)
+
+p1 = 0
+p2 = 0
+for start in g.find("0"):
+    queue = deque([start])
+    all = set()
+    while queue:
+        node = queue.popleft()
+        if g[node] == "9":
+            all.add(node)
+            p2 += 1
+
+        for nb in g.neighbors_ort(node):
+            if int(g[node]) + 1 == int(g[nb]):
+                queue.append(nb)
+    p1 += len(all)
+
+print(p1)
+print(p2)

2024/d11.py

@@ -0,0 +1,31 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__)
+xs = ints(data)
+CACHE = {}
+
+# I had maxsize too small at first :/
+# @lru_cache(maxsize=10**12) 
+def apply(x, rest):
+    if rest == 0:
+        return 1
+
+    if (x, rest) in CACHE:
+        return CACHE[(x, rest)]
+
+    if x == 0:
+        r = apply(1, rest - 1)
+    elif len(str(x)) % 2 == 0:
+        sx = str(x)
+        a = int(sx[: len(sx) // 2])
+        b = int(sx[len(sx) // 2 :])
+        r = apply(a, rest - 1) + apply(b, rest - 1)
+    else:
+        r = apply(x * 2024, rest - 1)
+    CACHE[(x, rest)] = r
+    return r
+
+
+print(sum([apply(x, 25) for x in xs]))
+print(sum([apply(x, 75) for x in xs]))

2024/d12.py

@@ -0,0 +1,61 @@
+from lib import get_data
+from lib import Grid2D
+from collections import defaultdict
+from collections import deque
+
+data = get_data(__file__)
+
+DIRS = {
+    "N": (-1, 0),
+    "E": (0, 1),
+    "S": (1, 0),
+    "W": (0, -1),
+}.values()
+
+
+g = Grid2D(data)
+cs = defaultdict(set)
+for row in range(g.n_rows):
+    for col in range(g.n_cols):
+        c = g[(row, col)]
+        cs[c].add((row, col))
+
+t1, t2 = 0, 0
+for c, cs in cs.items():
+    while cs:
+        peri = 0
+        start = cs.pop()
+        seen = set()
+        queue = deque([start])
+        fences = set()
+        while queue:
+            pos = queue.popleft()
+            if pos in seen:
+                continue
+            seen.add(pos)
+
+            for d in DIRS:
+                nb = d[0] + pos[0], d[1] + pos[1]
+                if g.contains(nb) and g[nb] == c:
+                    queue.append(nb)
+                    cs.discard(nb)
+                else:
+                    peri += 1
+                    nb = tuple(list(nb) + [d])
+                    fences.add(nb)
+
+        nfences = set()
+        for row, col, dir in fences:
+            for dr, dc in [(1, 0), (0, 1)]:
+                nr, nc = row + dr, col + dc
+                if (nr, nc, dir) in fences:
+                    break
+            else:
+                nfences.add((row, col, dir))
+
+        c_area = len(seen)
+        t1 += c_area * peri
+        t2 += c_area * len(nfences)
+
+print(t1)
+print(t2)

2024/d13.py

@@ -0,0 +1,33 @@
+from lib import get_data
+from lib import ints
+
+data = get_data(__file__)
+ps = data.split("\n\n")
+
+c1, c2 = 0, 0
+for p in ps:
+    lines = p.splitlines()
+    ax, ay = ints(lines[0])
+    bx, by = ints(lines[1])
+    px, py = ints(lines[2])
+    px2 = px + 10000000000000
+    py2 = py + 10000000000000
+
+    for a in range(0, 101):
+        for b in range(0, 101):
+            if a * ax + b * bx == px and a * ay + b * by == py:
+                c1 += a * 3 + b
+
+    D = ax * by - bx * ay
+    if abs(D) > 1e-10:
+        a_ = px2 * by - bx * py2
+        b_ = ax * py2 - px2 * ay
+        if a_ % D == 0 and b_ % D == 0:
+            a = (px2 * by - bx * py2) // D
+            b = (ax * py2 - px2 * ay) // D
+
+            if a >= 0 and b >= 0:
+                c2 += a * 3 + b
+
+print(c1)
+print(c2)

2024/d14.py

@@ -0,0 +1,64 @@
+from lib import get_data
+from lib import ints
+from collections import defaultdict
+
+rows = 103
+cols = 101
+data = get_data(__file__)
+
+
+def score(robots):
+    quadrants = defaultdict(int)
+    for _, r, c in robots:
+        if r < rows // 2 and c < cols // 2:
+            quadrants[1] += 1
+        elif r < rows // 2 and c > cols // 2:
+            quadrants[2] += 1
+        elif r > rows // 2 and c < cols // 2:
+            quadrants[3] += 1
+        elif r > rows // 2 and c > cols // 2:
+            quadrants[4] += 1
+    t = 1
+    for q in quadrants.values():
+        t *= q
+    return t
+
+
+def print_from_xy(xs):
+    x_min = min(v[1] for v in xs)
+    x_max = max(v[1] for v in xs)
+    y_min = min(v[0] for v in xs)
+    y_max = max(v[0] 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)
+
+
+robots_speed = {}
+robots = list()
+for i, line in enumerate(data.splitlines()):
+    c, r, vc, vr = ints(line)
+    robots_speed[i] = (vr, vc)
+    robots.append((i, r, c))
+
+for j in range(rows * cols):
+    nrobots = list()
+    count = 0
+    for i, r, c in robots:
+        vr, vc = robots_speed[i]
+        nr = (r + vr) % rows
+        nc = (c + vc) % cols
+        nrobots.append((i, nr, nc))
+    robots = nrobots
+    if j == 99:
+        print(score(robots))
+    robots_coords = [(r, c) for _, r, c in robots]
+    if len(robots_coords) == len(set(robots_coords)):
+        print(j + 1)
+        # print_from_xy(robots_coords)
+        break

2024/d15.py

@@ -0,0 +1,92 @@
+from lib import get_data
+from lib import Grid2D
+
+DIRS = {
+    "^": (-1, 0),
+    ">": (0, 1),
+    "v": (1, 0),
+    "<": (0, -1),
+}
+
+data = get_data(__file__)
+data, moves = data.split("\n\n")
+
+g = Grid2D(data)
+
+
+def simulate(grid: Grid2D, moves: str):
+    (p,) = g.find("@")
+    for c in moves:
+        if c == "\n":
+            continue
+        d = DIRS[c]
+
+        to_move = set([p])
+        row = to_move
+        blocked = False
+        while True:
+            nrow = set()
+            for (
+                r,
+                c,
+            ) in row:
+                np = r + d[0], c + d[1]
+                if g[np] == "#":
+                    blocked = True
+                elif g[np] == "O":
+                    nrow.add(np)
+                elif g[np] == "[":
+                    nrow.add(np)
+                    if d == (1, 0) or d == (-1, 0):
+                        nrow.add((np[0], np[1] + 1))
+                elif g[np] == "]":
+                    if d == (1, 0) or d == (-1, 0):
+                        nrow.add((np[0], np[1] - 1))
+                    nrow.add(np)
+            to_move |= row
+            row = nrow
+            if len(row) == 0 or blocked:
+                break
+
+        if not blocked:
+            to_place = {}
+            p = p[0] + d[0], p[1] + d[1]
+
+            for tm in to_move:
+                np = tm[0] + d[0], tm[1] + d[1]
+                to_place[np] = g[tm]
+                g[tm] = "."
+
+            for pos, c in to_place.items():
+                g[pos] = c
+
+
+def score(g: Grid2D) -> int:
+    os = g.find("O")
+    if os:
+        return sum(r * 100 + c for r, c in os)
+    return sum(r * 100 + c for r, c in g.find("["))
+
+
+simulate(g, moves)
+print(score(g))
+
+ndata = ""
+for c in data:
+    if c == "#":
+        ndata += "##"
+    elif c == "O":
+        ndata += "[]"
+    elif c == ".":
+        ndata += ".."
+    elif c == "@":
+        ndata += "@."
+    else:
+        ndata += c
+
+g = Grid2D(ndata)
+(p,) = g.find("@")
+
+simulate(g, moves)
+print(score(g))
+exit()

2024/d16.py

@@ -0,0 +1,96 @@
+import heapq
+from collections import defaultdict
+from lib import get_data
+from lib import Grid2D
+
+
+data = get_data(__file__)
+
+g = Grid2D(data)
+
+
+def search(start, end, dir):
+    paths = set()
+
+    def reconstruct(parents, current):
+        seen = set()
+        to_visit = [current]
+        while to_visit:
+            current = to_visit.pop()
+            if current in seen:
+                continue
+            seen.add(current)
+            paths.add(current[0])
+            for p in parents[current]:
+                to_visit.append(p)
+
+    def dist(n1, n2):
+        """cost from node to node"""
+        if n1 == 0 or n1 == n2:
+            return 0
+        p1, d1 = n1
+        p2, d2 = n2
+        if p1 != p2:
+            return 1
+        if d1 != d2:
+            return 1000
+        assert False
+
+    def h(node):
+        """heuristic function (never overestimate)"""
+        pos = node[0]
+        return abs(pos[0] - end[0]) + abs(pos[1] - end[1])
+
+    def is_goal(node):
+        return node[0] == end
+
+    def neighbors(node):
+        pos, dir = node
+        npos = pos[0] + dir[0], pos[1] + dir[1]
+        nbs = []
+        if g.contains(npos) and g[npos] != "#":
+            nbs.append((npos, dir))
+        ndir = dir[1], -dir[0]
+        nbs.append((pos, ndir))
+        ndir = -dir[1], dir[0]
+        nbs.append((pos, ndir))
+        return nbs
+
+    starts = [(start, dir)]
+    open_set = []
+    g_score = {}
+    cost = None
+
+    for start in starts:
+        heapq.heappush(open_set, (h(start), start))
+        g_score[start] = dist(0, start)
+
+    parents = defaultdict(list)
+    while open_set:
+        current_f_score, current = heapq.heappop(open_set)
+        if is_goal(current):
+            # assert current_f_score == g_score[current]
+            gs = g_score[current]
+            if cost is None or gs <= cost:
+                cost = gs
+                reconstruct(parents, current)
+            else:
+                break
+
+        for neighbor in neighbors(current):
+            tentative_g_score = g_score[current] + dist(current, neighbor)
+            if tentative_g_score <= g_score.get(neighbor, 10**12):
+                parents[neighbor].append(current)
+                g_score[neighbor] = tentative_g_score
+                f_score = g_score[neighbor] + h(neighbor)
+                heapq.heappush(open_set, (f_score, neighbor))
+    return cost, paths
+
+
+(start,) = g.find("S")
+(end,) = g.find("E")
+dir = (0, 1)
+
+cost, paths = search(start, end, dir)
+print(cost)
+print(len(paths))

2024/d17.py

@@ -0,0 +1,61 @@
+from lib import get_data
+from lib import ints
+
+
+data = get_data(__file__)
+nums, prog = data.split("\n\n")
+regs = ints(nums)
+prog = ints(prog)
+
+i = 0
+out = []
+while i < len(prog) - 1:
+    inst, op = prog[i], prog[i + 1]
+    assert op != 7
+    combo = op if op not in [4, 5, 6] else regs[op - 4]
+    literal = op
+    match inst:
+        case 0:
+            regs[0] = regs[0] >> combo
+        case 1:
+            regs[1] = regs[1] ^ literal
+        case 2:
+            regs[1] = combo % 8
+        case 3:
+            if regs[0] != 0:
+                i = literal - 2
+        case 4:
+            regs[1] = regs[1] ^ regs[2]
+        case 5:
+            out.append(combo % 8)
+        case 6:
+            regs[1] = regs[0] // (2**combo)
+        case 7:
+            regs[2] = regs[0] // (2**combo)
+        case _:
+            assert False
+    i += 2
+
+print(",".join(map(str, out)))
+
+
+def get_a(a_current, xs):
+    if len(xs) == 0:
+        return [a_current // 8]
+    x = xs[0]
+    aan = []
+    for a_new in range(8):
+        a = a_current + a_new
+        b = a % 8
+        assert b == a_new
+        b = b ^ 1
+        c = a >> b
+        b = b ^ c
+        b = b ^ 5
+        if (b % 8) == x:
+            aan += get_a(a << 3, xs[1:])
+    return aan
+
+
+aa = get_a(0, list(reversed(prog)))
+print(min(aa))