advent-of-code/2023/day15.py

import sys
from functools import reduce

steps = sys.stdin.read().strip().split(",")


def _hash(s: str) -> int:
    return reduce(lambda v, u: ((v + ord(u)) * 17) % 256, s, 0)


# part 1
answer_1 = sum(map(_hash, steps))
print(f"answer 1 is {answer_1}")

# part 2
boxes: list[dict[str, int]] = [{} for _ in range(256)]

for step in steps:
    if (i := step.find("=")) >= 0:
        label, length = step[:i], int(step[i + 1 :])
        boxes[_hash(label)][label] = length
    else:
        label = step[:-1]
        boxes[_hash(label)].pop(label, None)

answer_2 = sum(
    i_box * i_lens * length
    for i_box, box in enumerate(boxes, start=1)
    for i_lens, length in enumerate(box.values(), start=1)
)
print(f"answer 2 is {answer_2}")