Advent of code 2023 day 5 old

def day5(s, *, part2=False):
  sections = s.split('\n\n')
  (line,) = sections[0].splitlines()
  values = map(int, line.split(': ')[1].split())
  if part2:
    intervals = [(start, start + n) for start, n in more_itertools.batched(values, 2)]
  else:
    intervals = [(start, start + 1) for start in values]

  def remap(start, stop, lines):
    if not lines:
      yield start, stop
    else:
      dst, src, num = map(int, lines[0].split())
      i0, i1 = max(src, start), min(src + num, stop)
      if i0 < i1:
        yield dst + (i0 - src), dst + (i1 - src)
      if i0 > start:
        yield from remap(start, min(i0, stop), lines[1:])
      if i1 < stop:
        yield from remap(max(i1, start), stop, lines[1:])

  for section in sections[1:]:
    lines = section.splitlines()[1:]
    chain = itertools.chain.from_iterable
    intervals = list(chain(remap(*interval, lines) for interval in intervals))

  return min(start for start, _ in intervals)