2023/day15.py

import os
import sys
from collections import defaultdict


def hash(s: str) -> int:
    v = 0
    for c in s:
        if c == ",":
            continue
        v += ord(c)
        v *= 17
        v %= 256
    return v


def main() -> None:
    with open(sys.argv[1]) as f:
        s = f.read().strip()

    boxes: defaultdict[int, list[tuple[str, int]]] = defaultdict(list)

    part1 = 0
    for s_ in s.split(","):
        part1 += hash(s_)

        if s_[-1] == "-":
            label = s_[:-1]
            h = hash(label)
            for i in range(len(boxes[h])):
                if boxes[h][i][0] == label:
                    del boxes[h][i]
                    break
        elif s_[-2] == "=":
            label = s_[:-2]
            focal = int(s_[-1])
            h = hash(label)
            for i in range(len(boxes[h])):
                if boxes[h][i][0] == label:
                    boxes[h][i] = (label, focal)
                    break
            else:
                boxes[h].append((label, focal))

    part2 = 0
    for (box_i, box) in boxes.items():
        for (slot, (_, focal)) in enumerate(box):
            part2 += (box_i + 1) * (slot + 1) * focal

    print(part1, part2)


if __name__ == "__main__":
    main()