Advent of code 2025 day 9

def day9(s, *, part2=False):
  points = [tuple(map(int, line.split(','))) for line in s.splitlines()]
  pairs = [
      (min(x1, x2), min(y1, y2), max(x1, x2), max(y1, y2))
      for (x1, y1), (x2, y2) in itertools.combinations(points, 2)
  ]

  def area(x1, y1, x2, y2):
    return (x2 - x1 + 1) * (y2 - y1 + 1)

  if not part2:
    return max(area(*pair) for pair in pairs)

  edges = [
      (min(x1, x2), min(y1, y2), max(x1, x2), max(y1, y2))
      for (x1, y1), (x2, y2) in itertools.pairwise(points + [points[0]])
  ]
  length = lambda p: p[2] - p[0] + p[3] - p[1]
  edges = sorted(edges, key=length, reverse=True)  # Optional, provides 4x speedup.

  return max(
      area(x1, y1, x2, y2)
      for x1, y1, x2, y2 in pairs
      if all(xx1 >= x2 or xx2 <= x1 or yy1 >= y2 or yy2 <= y1 for xx1, yy1, xx2, yy2 in edges)
  )