Advent of Code 2023 - Day 12

day_23_12.py

from functools import lru_cache

type Group = tuple[int, ...]
type Result = tuple[int, int]
type SpringConfiguration = tuple[str, Group]

OPERATIONAL = "."
DAMAGED = "#"


@lru_cache(maxsize=None)
def arrangements(
    springs: str, groups: Group, current=0, current_count=0, processed=0
) -> int:
    if current == len(springs):
        return 1 if len(groups) == processed else 0

    if springs[current] == DAMAGED:
        return arrangements(springs, groups, current + 1, current_count + 1, processed)

    if springs[current] == OPERATIONAL or processed == len(groups):
        if processed < len(groups) and current_count == groups[processed]:
            return arrangements(springs, groups, current + 1, 0, processed + 1)
        return (
            arrangements(springs, groups, current + 1, 0, processed)
            if not current_count
            else 0
        )

    damaged = arrangements(springs, groups, current + 1, current_count + 1, processed)

    match current_count:
        case count if count == groups[processed]:
            return damaged + arrangements(
                springs, groups, current + 1, 0, processed + 1
            )
        case 0:
            return damaged + arrangements(springs, groups, current + 1, 0, processed)
        case _:
            return damaged


def parse_input(year, day) -> list[SpringConfiguration]:
    def get_spring(i):
        [spring, count_str] = i.split(" ")
        return (spring, tuple([int(i) for i in count_str.split(",")]))

    with open(f"../input_files/{year}_{day}.txt") as f:
        return list(map(get_spring, f.readlines()))


def run(input_data: list[SpringConfiguration]) -> Result:
    part_1 = sum(arrangements(spring + ".", groups) for spring, groups in input_data)
    part_2 = sum(
        arrangements("?".join([spring] * 5) + ".", groups * 5)
        for spring, groups in input_data
    )

    return (part_1, part_2)


if __name__ == "__main__":
    input_data = parse_input(2023, 12)
    print(run(input_data))