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๐ช - 2023 DAY 14 SOLUTIONS -๐ช
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this post was submitted on 14 Dec 2023
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Advent Of Code
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An unofficial home for the advent of code community on programming.dev! Other challenges are also welcome!
Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.
Everybody Codes is another collection of programming puzzles with seasonal events.
EC 2025
AoC 2025
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| 8 | 9 | 10 | 11 | 12 |
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Nim
Getting caught up slowly after spending way too long on day 12. I'll be busy this weekend though, so I'll probably fall further behind.
Part 2 looked daunting at first, as I knew brute-forcing 1 billion iterations wouldn't be practical. I did some premature optimization anyway, pre-calculating north/south and east/west runs in which the round rocks would be able to travel.
At first I figured maybe the rocks would eventually reach a stable configuration, so I added a check to detect if the current iteration matches the previous one. It never triggered, so I dumped some of the grid states and it became obvious that there was a cycle occurring. I probably should have guessed this in advance. The spin cycle is effectively a pseudorandom number generator, and all PRNGs eventually cycle. Good PRNGs have a very long cycle length, but this one isn't very good.
I added a hash table, mapping the state of each iteration to the next one. Once a value is added that already exists in the table as a key, there's a complete cycle. At that point it's just a matter of walking the cycle to determine it's length, and calculating from there.
Hi there! Looks like you linked to a Lemmy community using a URL instead of its name, which doesn't work well for people on different instances. Try fixing it like this: !nim@programming.dev