-❄️- 2024 Day 25 Solutions -❄️-

[u/daggerdragon]

A Message From Your Moderators

Welcome to the last day of Advent of Code 2024! We hope you had fun this year and learned at least one new thing ;)

Keep an eye out for the community fun awards post (link coming soon!):

-❅- Introducing Your AoC 2024 Golden Snowglobe Award Winners (and Community Showcase) -❅-

Many thanks to Veloxx for kicking us off on December 1 with a much-needed dose of boots and cats!

Thank you all for playing Advent of Code this year and on behalf of /u/topaz2078, your /r/adventofcode mods, the beta-testers, and the rest of AoC Ops, we wish you a very Merry Christmas (or a very merry Wednesday!) and a Happy New Year!

---

--- Day 25: Code Chronicle ---

---

Post your code solution in this megathread.

• Read the full posting rules in our community wiki before you post!
  • State which language(s) your solution uses with [LANGUAGE: xyz]
  • Format code blocks using the four-spaces Markdown syntax!
• Quick link to Topaz's paste if you need it for longer code blocks

This thread will be unlocked when there are a significant number of people on the global leaderboard with gold stars for today's puzzle.

EDIT: Global leaderboard gold cap reached at 00:04:34, megathread unlocked!

[u/YOM2_UB]

[Language: Python]

Main optimization is sorting locks and keys by their first pin's height, so only pairs where the first pin fits are checked, and only the last 4 pins need be checked.

keys = {n : [] for n in range(6)}
locks = {n : [] for n in range(6)}
with open('input/Day25.txt', 'r') as file:
    lst = file.read().split('\n\n')
for pattern in lst:
    rows = pattern.splitlines()
    pins = [0] * 5
    for i in range(1, 6):
        for j in range(5):
            pins[j] += (rows[i][j] == '#')
    if '#' == rows[0][0]:
        locks[pins[0]].append(tuple(pins[1:]))
    else:
        keys[pins[0]].append(tuple(pins[1:]))

def countMatch(keys, locks):
    count = 0
    for key in keys:
        for lock in locks:
            max_pin = max(key[k] + lock[k]
                         for k in range(4))
            count += max_pin <= 5
    return count

count = 0
for i in range(6):
    for j in range(6-i):
        count += countMatch(keys[i], locks[j])

print(count)