Solve day 20.

2017/d18.py

@@ -0,0 +1,109 @@
+from lib import LETTERS_LOWER
+from collections import defaultdict, deque
+
+
+def get_value(regs, val):
+    if val in LETTERS_LOWER:
+        return regs[val]
+    return int(val)
+
+
+def part_1(data):
+    regs = defaultdict(int)
+    insts = data.splitlines()
+    last_sound = None
+    pc = 0
+    while pc <= len(insts):
+        cmds = insts[pc].split()
+        match cmds:
+            case ["set", reg, val]:
+                val = get_value(regs, val)
+                regs[reg] = val
+            case ["mul", reg, val]:
+                val = get_value(regs, val)
+                regs[reg] = regs[reg] * val
+            case ["add", reg, val]:
+                val = get_value(regs, val)
+                regs[reg] = regs[reg] + val
+            case ["mod", reg, val]:
+                val = get_value(regs, val)
+                regs[reg] = regs[reg] % val
+            case ["rcv", val]:
+                if get_value(regs, val) != 0:
+                    print(last_sound)
+                    return
+            case ["snd", val]:
+                last_sound = get_value(regs, val)
+            case ["jgz", cnd, off]:
+                if get_value(regs, cnd) > 0:
+                    pc += get_value(regs, off) # XXX?
+                    continue
+            case _:
+                print(cmds)
+                assert False
+        pc += 1
+
+        
+def part_2(data):
+    progs = []
+    insts = data.splitlines()
+    prog1_counter = 0
+
+    for i in [0, 1]:
+        regs = defaultdict(int)
+        regs["p"] = i
+        pc = 0
+        progs.append([pc, regs, False, deque()])
+
+    while not all(prog[2] for prog in progs):
+        for prog in progs:
+            pc, regs, waiting, queue = prog
+
+            cmds = insts[pc].split()
+            match cmds:
+                case ["set", reg, val]:
+                    val = get_value(regs, val)
+                    regs[reg] = val
+                case ["mul", reg, val]:
+                    val = get_value(regs, val)
+                    regs[reg] = regs[reg] * val
+                case ["add", reg, val]:
+                    val = get_value(regs, val)
+                    regs[reg] = regs[reg] + val
+                case ["mod", reg, val]:
+                    val = get_value(regs, val)
+                    regs[reg] = regs[reg] % val
+                case ["rcv", reg]:
+                    if queue:
+                        val = queue.popleft()
+                        regs[reg] = val
+                    else:
+                        prog[2] = True
+                        pc -= 1
+                case ["snd", val]:
+                    val = get_value(regs, val)
+                    if prog == progs[0]:
+                        other_prog = progs[1]
+                    else:
+                        prog1_counter += 1
+                        other_prog = progs[0]
+                    other_prog[3].append(val)
+                case ["jgz", cnd, off]:
+                    if get_value(regs, cnd) > 0:
+                        pc += get_value(regs, off) # XXX?
+                        pc -= 1
+                case _:
+                    print(cmds)
+                    assert False
+            prog[0] = pc + 1
+    print(prog1_counter)
+
+
+def main():
+    data = open(0).read().strip()
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2017/d19.py

@@ -0,0 +1,50 @@
+from lib import Grid2D, LETTERS_UPPER, add2, sub2
+
+
+def part_1(data):
+    g = Grid2D(data)
+    g.print()
+
+    current = None
+    for c in range(g.n_cols):
+        if g[(0, c)] == "|":
+            current = (0, c)
+
+    current_dir = Grid2D.S
+    letters = ""
+    done = False
+    steps = 0
+
+    while not done:
+        while g[current] != " ":
+            current = add2(current, current_dir)
+            steps += 1
+            if g[current] in LETTERS_UPPER:
+                letter = g[current]
+                if letter in letters:
+                    done = True
+                    break
+                letters += letter
+
+            if g[current] == "+":
+                break
+
+        next_field = None
+        for nb in g.neighbors_ort(current):
+            if nb != sub2(current, current_dir) and (g[nb] in "-|" or g[nb] in LETTERS_UPPER):
+                next_field = nb
+        if next_field is None:
+            done = True
+        else:
+            current_dir = sub2(next_field, current)
+    print(letters)
+    print(steps)
+
+
+def main():
+    data = open(0).read()
+    part_1(data)
+
+
+if __name__ == "__main__":
+    main()

2017/d20.py

@@ -0,0 +1,55 @@
+from lib import str_to_ints
+from collections import defaultdict
+
+
+def part_1(data):
+    ps = []
+    for i, line in enumerate(data.splitlines()):
+        ps.append(str_to_ints(line) + [i])
+
+    for _ in range(10_000):
+        for p in ps:
+            p[3] += p[6]
+            p[4] += p[7]
+            p[5] += p[8]
+            p[0] += p[3]
+            p[1] += p[4]
+            p[2] += p[5]
+    
+    ps.sort(key=lambda p: abs(p[0]) + abs(p[1]) + abs(p[2]))
+    print(ps[0][-1])
+
+
+def part_2(data):
+    ps = []
+    for i, line in enumerate(data.splitlines()):
+        ps.append(str_to_ints(line) + [i])
+
+    for _ in range(10_000):
+        poss = defaultdict(list)
+
+        for p in ps:
+            p[3] += p[6]
+            p[4] += p[7]
+            p[5] += p[8]
+            p[0] += p[3]
+            p[1] += p[4]
+            p[2] += p[5]
+            poss[(p[0], p[1], p[2])].append(p)
+
+        for pts in poss.values():
+            if len(pts) > 1:
+                for p in pts:
+                    ps.remove(p)
+    
+    print(len(ps))
+
+
+def main():
+    data = open(0).read()
+    part_1(data)
+    part_2(data)
+
+
+if __name__ == "__main__":
+    main()

2017/lib.py

@@ -27,6 +27,9 @@ def mape(f, xs):
 def add2(a: tuple[int, int], b: tuple[int, int]) -> tuple[int, int]:
     return (a[0] + b[0], a[1] + b[1])
 
+def sub2(a: tuple[int, int], b: tuple[int, int]) -> tuple[int, int]:
+    return (a[0] - b[0], a[1] - b[1])
+
 class Grid2D:
     N = (-1, 0)
     E = (0, 1)

README.md

@@ -77,4 +77,8 @@ written in Python.
 - Day 14: 17:48
 - Day 15: 11:40
 - Day 16: 13:16
-- Day 17: 
+- Day 17: 55:00
+- Day 18: 23:00
+- Day 19: 45:00
+- Day 20: 9:55 (would have been 10th)
+- Day 21: