aoc-21 VS aoc2021

C++ 17 solution, part 1 & part 2 run at 129ms [Github](https://github.com/giorgosioak/aoc-21/tree/main/21)

My modern C++ solution github ( compiled C++17 )

thanks to Andrew's suggestion

I've done every year in Haskell (2015 2016 2017 2018 2019 2020 2021), and so have several other people such as /u/glguy. I don't see if /u/mstksg has anything published for 2015 but they've done 2016 2017 2018 2019 2020 2021 along with some pretty good writeups, I recommend checking those out.

I ran my own benchmarks for a whole ton of code at https://github.com/ephemient/aoc2021 on both Linux x64 and macos x64, and ended up disabling Kotlin/Native because it was varying between 10x and 100x slower than Kotlin/JVM, eventually timing out on CI. The generated code may be reasonable thanks to LLVM, but the runtime certainly is not.

Took a while for me to get around to completing this in Kotlin, Python, and Rust as well, since I was working on optimizing other solutions, but I finally made it.

So I switched tacks and implemented this in Kotlin, where mutation is easier. First version was brute-force with duplicate state avoidance (checked before the state explosion at every input), which worked quickly enough for part 1, but ran into OOMs for part 2. Once I replaced the HashSet with a custom LruSet (and later a simpler CacheSet which simply overwrites on hash collisions) it ran part 2 in a few minutes. I then ported this into Haskell.

Haskell 1171/339

Kotlin, Python, and Rust solutions are the same solution but much uglier.

I'm doing the same cached recursion in Kotlin, Python, and Rust.

Haskell 621/603

Haskell 258/240

Haskell Kotlin 622/1185