this post was submitted on 16 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!
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.
AoC 2023
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console.log('Hello World')
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Rust
I simply check each starting position individually for Part 2, I don't know if there are more clever solutions. Initially that approach ran in 180ms which is a lot more than any of the previous puzzles needed, so I tried if I could optimize it.
Initially I was using two hash sets, one for counting unique energized fields, and one for detecting cycles which also included the direction in the hash. Going from the default rust hasher to FxHash sped it up to 100ms. Seeing that, I thought that this point could be further improved upon, and ended up replacing both hash sets with boolean arrays, since their size is neatly bounded by the input field size. Now it runs in merely 30ms, meaning a 6x speedup just by getting rid of the hashing.