Advent of code 2023 day 9

def day9(s, *, part2=False):

  def f(a):
    return 0 if not any(a) else a[0] - f(np.diff(a)) if part2 else a[-1] + f(np.diff(a))

  return sum(f(np.array(line.split(), int)) for line in s.splitlines())