Advent of code 2024 day 12

def day12(s, *, part2=False):
  grid = np.array([list(line) for line in s.splitlines()])
  grid = np.pad(grid, 1, constant_values='.')
  visited = grid == '.'
  total = 0

  for (y, x), ch in np.ndenumerate(grid):
    if visited[y, x]:
      continue
    visited[y, x] = True
    area = perimeter = sides = 0
    stack = [(y, x)]
    while stack:
      y, x = stack.pop()
      area += 1
      sames = []
      for dy, dx in ((-1, 0), (0, -1), (1, 0), (0, 1)):
        ny, nx = y + dy, x + dx
        same = grid[ny, nx] == ch
        sames.append((dy, dx, same))
        if same:
          if not visited[ny, nx]:
            visited[ny, nx] = True
            stack.append((ny, nx))
        else:
          perimeter += 1
      sames.append(sames[0])
      for (dy1, dx1, same1), (dy2, dx2, same2) in itertools.pairwise(sames):
        sides += (
            (not same1 and not same2)
            or (same1 and same2 and grid[y + dy1 + dy2, x + dx1 + dx2] != ch)
        )

    total += area * (sides if part2 else perimeter)

  return total