Advent of code 2023 day 5

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]

  for section in sections[1:]:
    output_intervals = []
    for line in section.splitlines()[1:]:
      dst, src, num = map(int, line.split())
      new_intervals = []
      for start, stop in intervals:
        i0, i1 = max(src, start), min(src + num, stop)
        if i0 < i1:
          output_intervals.append((dst + (i0 - src), dst + (i1 - src)))
        if i0 > start:
          new_intervals.append((start, min(i0, stop)))
        if i1 < stop:
          new_intervals.append((max(i1, start), stop))
      intervals = new_intervals
    intervals.extend(output_intervals)

  return min(start for start, _ in intervals)