aoc

Advent of Code
git clone https://git.pngu.org/aoc
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24_2020.py (1648B)

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import re
import sys

L = sys.stdin.read().strip().split("\n")
B = set()
for l in L:
    x, y, z = 0, 0, 0
    i = 0
    while l:
        if l.startswith("e"):
            x += 1
            y -= 1
            l = l[1:]
        elif l.startswith("se"):
            y -= 1
            z += 1
            l = l[2:]
        elif l.startswith("sw"):
            x -= 1
            z += 1
            l = l[2:]
        elif l.startswith("w"):
            x -= 1
            y += 1
            l = l[1:]
        elif l.startswith("nw"):
            z -= 1
            y += 1
            l = l[2:]
        elif l.startswith("ne"):
            x += 1
            z -= 1
            l = l[2:]
        else:
            assert False
    if (x, y, z) in B:
        B.remove((x, y, z))
    else:
        B.add((x, y, z))
print(len(B))

for _ in range(100):
    newB = set()
    CHECK = set()
    for x, y, z in B:
        CHECK.add((x, y, z))
        for dx, dy, dz in [
            (1, -1, 0),
            (0, -1, 1),
            (-1, 0, 1),
            (-1, 1, 0),
            (0, 1, -1),
            (1, 0, -1),
        ]:
            CHECK.add((x + dx, y + dy, z + dz))

    for x, y, z in CHECK:
        nbr = 0
        for dx, dy, dz in [
            (1, -1, 0),
            (0, -1, 1),
            (-1, 0, 1),
            (-1, 1, 0),
            (0, 1, -1),
            (1, 0, -1),
        ]:
            if (x + dx, y + dy, z + dz) in B:
                nbr += 1
        if (x, y, z) in B and (nbr == 1 or nbr == 2):
            newB.add((x, y, z))
        if (x, y, z) not in B and nbr == 2:
            newB.add((x, y, z))
    B = newB
print(len(B))