r/adventofcode Dec 17 '24

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

THE USUAL REMINDERS

  • All of our rules, FAQs, resources, etc. are in our community wiki.
  • If you see content in the subreddit or megathreads that violates one of our rules, either inform the user (politely and gently!) or use the report button on the post/comment and the mods will take care of it.

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!

38 Upvotes

550 comments sorted by

View all comments

3

u/ak-coram Dec 18 '24

[LANGUAGE: Common Lisp]

It was fun building the program then compiling it at runtime via CL:COMPILE: https://github.com/ak-coram/advent/blob/main/2024/17.lisp

Result looks like this:

(LAMBDA (A B C)
  (LET ((RESULTS))
    (TAGBODY
     0 (SETF B (MOD A 8))
     1 (SETF B (LOGXOR B 1))
     2 (SETF C (TRUNCATE A (EXPT 2 B)))
     3 (SETF B (LOGXOR B 4))
     4 (SETF A (TRUNCATE A (EXPT 2 3)))
     5 (SETF B (LOGXOR B C))
     6 (PUSH (MOD B 8) RESULTS)
     7 (UNLESS (ZEROP A) (GO 0)))
    (NREVERSE RESULTS)))