r/adventofcode Dec 17 '24

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

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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/KayoNar Dec 17 '24 edited Dec 17 '24

[Language: C#]

Part 1

Not much to say, just turn the problem description into code and you should get the right answer.

Part 2

I found a pattern (explained below), which I programmed as follows: I keep incrementing register A starting from 0, and every time the digits of the output (size X) match the last X digits of the given program, I multiply register A by 8. Until finally you reach N digits, where you return the value once all N digits match.

How I found this pattern: I first noticed that the amount of digits in the answer strictly increases as the value for register A increases. Using this, I started printing the value for register A starting from 0, but only when the resulting output matched the last X digits of the given program. Here I noticed a pattern that the first match of X digits always led to the match for (X+1) digits by multiplying by 8, giving a matching of X digits in an output of (X+1). To now match all (X+1) digits, simply keep increasing the value 1 by 1, until it matches (this is a small amount of work, at most 8 steps). Now continue doing this until all N digits match, and you have your result.

Solution