Python

After a bunch of fiddling yesterday and today I finally managed to arrive at a regex-only solution for part 2. That re.DOTALL is crucial here.

import re
from pathlib import Path


def parse_input_one(input: str) -> list[tuple[int]]:
    p = re.compile(r"mul\((\d{1,3}),(\d{1,3})\)")
    return [(int(m[0]), int(m[1])) for m in p.findall(input)]


def parse_input_two(input: str) -> list[tuple[int]]:
    p = re.compile(r"don't\(\).*?do\(\)|mul\((\d{1,3}),(\d{1,3})\)", re.DOTALL)
    return [(int(m[0]), int(m[1])) for m in p.findall(input) if m[0] and m[1]]


def part_one(input: str) -> int:
    pairs = parse_input_one(input)
    return sum(map(lambda v: v[0] * v[1], pairs))


def part_two(input: str) -> int:
    pairs = parse_input_two(input)
    return sum(map(lambda v: v[0] * v[1], pairs))


if __name__ == "__main__":
    input = Path("input").read_text("utf-8")
    print(part_one(input))
    print(part_two(input))