Advent of code 2022 day 23

def day23(s, *, part2=False):
  grid = np.array([list(line) for line in s.splitlines()])
  current = set(tuple(yx) for yx in np.argwhere(grid == '#'))
  offsets8 = set(itertools.product((-1, 0, 1), repeat=2)) - {(0, 0)}
  dirs = [(-1, 0), (1, 0), (0, -1), (0, 1)]

  for round_index in range(10**8 if part2 else 10):
    proposed = {}
    for y, x in current:
      if any((y + dy, x + dx) in current for dy, dx in offsets8):
        for dy, dx in dirs:
          neighb3 = [tuple((i if c == 0 else c) for c in (dy, dx)) for i in (-1, 0, 1)]
          if not any((y + dy2, x + dx2) in current for dy2, dx2 in neighb3):
            proposed[y, x] = y + dy, x + dx
            break

    dirs = dirs[1:] + dirs[0:1]
    counter = collections.Counter(proposed.values())
    if part2 and 1 not in counter.values():
      return round_index + 1  # Motivation for increment by 1 is unclear.

    for yx in current.copy():
      if yx in proposed and counter[proposed[yx]] == 1:
        current.remove(yx)
        current.add(proposed[yx])

  return np.prod(np.ptp(list(current), 0) + 1) - len(current)