day24.py

#!/usr/bin/env python3

import os
import sys
import random
import re
import numpy as np
from collections import defaultdict

src = open("input.txt", "r").readlines()
src2 = """sesenwnenenewseeswwswswwnenewsewsw
neeenesenwnwwswnenewnwwsewnenwseswesw
seswneswswsenwwnwse
nwnwneseeswswnenewneswwnewseswneseene
swweswneswnenwsewnwneneseenw
eesenwseswswnenwswnwnwsewwnwsene
sewnenenenesenwsewnenwwwse
wenwwweseeeweswwwnwwe
wsweesenenewnwwnwsenewsenwwsesesenwne
neeswseenwwswnwswswnw
nenwswwsewswnenenewsenwsenwnesesenew
enewnwewneswsewnwswenweswnenwsenwsw
sweneswneswneneenwnewenewwneswswnese
swwesenesewenwneswnwwneseswwne
enesenwswwswneneswsenwnewswseenwsese
wnwnesenesenenwwnenwsewesewsesesew
nenewswnwewswnenesenwnesewesw
eneswnwswnwsenenwnwnwwseeswneewsenese
neswnwewnwnwseenwseesewsenwsweewe
wseweeenwnesenwwwswnew""".splitlines()
src = [r.strip() for r in src if r.strip()]

skew = 2  # 1.8 is more "hexagonal"

vecs = {
    "e": np.array([2, 0]),
    "se": np.array([1, -skew]),
    "sw": np.array([-1, -skew]),
    "w": np.array([-2, 0]),
    "nw": np.array([-1, skew]),
    "ne": np.array([1, skew]),
}

tiles = defaultdict(int)

for line in src:
    x = [vecs[m] for m in re.findall(r"(e|se|sw|w|nw|ne)", line)]

    tiles[tuple(np.sum(x, axis=0).round(1))] += 1

black = set()

for t, c in tiles.items():
    if c % 2 == 1:
        black.add(t)

print("part1:", len(black))


def get_adj(t):
    adj = set()
    for v in vecs.values():
        adj.add(tuple(np.sum([t, v], axis=0).round(1)))
    assert len(adj) == 6
    return adj


def turn():
    global black

    black_copy = set()

    for t in black:
        ta = get_adj(t)

        c = len(black.intersection(ta))
        if c == 1 or c == 2:
            black_copy.add(t)

        for w in ta.difference(black):
            c = len(black.intersection(get_adj(w)))
            if c == 2:
                black_copy.add(w)

    black = black_copy


for i in range(100):
    print(i)
    turn()

print("part2:", len(black))