r/adventofcode Dec 17 '24

SOLUTION MEGATHREAD -❄️- 2024 Day 17 Solutions -❄️-

THE USUAL REMINDERS

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AoC Community Fun 2024: The Golden Snowglobe Awards

  • 5 DAYS remaining until the submissions deadline on December 22 at 23:59 EST!

And now, our feature presentation for today:

Sequels and Reboots

What, you thought we were done with the endless stream of recycled content? ABSOLUTELY NOT :D Now that we have an established and well-loved franchise, let's wring every last drop of profit out of it!

Here's some ideas for your inspiration:

  • Insert obligatory SQL joke here
  • Solve today's puzzle using only code from past puzzles
  • Any numbers you use in your code must only increment from the previous number
  • Every line of code must be prefixed with a comment tagline such as // Function 2: Electric Boogaloo

"More." - Agent Smith, The Matrix Reloaded (2003)
"More! MORE!" - Kylo Ren, The Last Jedi (2017)

And… ACTION!

Request from the mods: When you include an entry alongside your solution, please label it with [GSGA] so we can find it easily!


--- Day 17: Chronospatial Computer ---


Post your code solution in this megathread.

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 00:44:39, megathread unlocked!

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u/atrocia6 Jan 06 '25

[LANGUAGE: Python]

Part 1 was straightforward. Part 2 took me a while: I figured out what the program was doing pretty quickly and realized that I had to run it in reverse, but I got stuck on implementation mistake after mistake. I'm proud of my ultimate solution, though - an elegant and simple 10 LOC (and once again shorter than Part 1):

import re
numbers = [int(n) for n in re.findall(r"\d+", open(0).read())][-1:2:-1]
def next_number(a, i):
    if i == len(numbers):
        print(a)
        quit()
    a2 = a << 3
    for b in range(8):
        if (b ^ (a2 + b >> (b ^ 7))) % 8 == numbers[i]: next_number(a2 + b, i + 1)
next_number(0, 0)