Advent of code 2024 day 11

def day11(s, *, part2=False):

  @functools.cache
  def length(e: str, num_steps: int) -> int:
    if num_steps == 0:
      return 1
    if e == '0':
      return length('1', num_steps - 1)
    if len(e) % 2 == 0:
      e1, e2 = e[: len(e) // 2], (e[len(e) // 2 :].lstrip('0') or '0')
      return length(e1, num_steps - 1) + length(e2, num_steps - 1)
    return length(str(int(e) * 2024), num_steps - 1)

  return sum(length(e, (25, 75)[part2]) for e in s.split())