aoc-2020/24.py

input = []

with open("24.input") as f:
    for line in f.readlines():
        seq = []
        i = iter(list(line.strip()))
        c1 = next(i, None)
        while c1 != None:
            if c1 in ['s', 'n']:
                seq.append(c1 + next(i))
            else:
                seq.append(c1)
            c1 = next(i, None)
        input.append(seq)

def get_pos(seq):
    pos = [0, 0]
    for move in seq:
        if move == 'w':
            pos[0] -= 2
        elif move == 'e':
            pos[0] += 2
        else:
            if move[0] == 's':
                pos[1] += 1
            else:
                pos[1] -= 1
            if move[1] == 'w':
                pos[0] -= 1
            else:
                pos[0] += 1
    return tuple(pos)

counts = {}

for seq in input:
    pos = get_pos(seq)
    if pos not in counts:
        counts[pos] = 0
    counts[pos] += 1

print("Answer 1:", len([v for v in counts.values() if v % 2 == 1]))

def count_adjacent(map, pos):
    x, y = pos
    adjacent = [(-2, 0), (2, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
    return len([1 for (off_x, off_y) in adjacent if map.get((x + off_x, y + off_y), False)])

map = {k: v % 2 == 1 for (k, v) in counts.items()}
max_x = max([abs(x) for (x, y) in map.keys()]) + 1
max_y = max([abs(y) for (x, y) in map.keys()]) + 1

for i in range(0, 100):
    next_map = {}
    for x in range(-max_x, max_x + 1):
        for y in range(-max_y, max_y + 1):
            if (x + y) % 2 == 1:
                continue
            count = count_adjacent(map, (x, y))
            if map.get((x, y), False) == True:
                next_map[(x, y)] = count in [1, 2]
            else:
                next_map[(x, y)] = count == 2
    map = next_map
    max_y += 1
    max_x += 2
    #print("Day {}: {}".format(i + 1, sum([1 for v in map.values() if v])))

print("Answer 2:", sum([1 for v in map.values() if v]))