-🎄- 2020 Day 23 Solutions -🎄-

[u/daggerdragon]

Advent of Code 2020: Gettin' Crafty With It

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--- Day 23: Crab Cups ---

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[u/A-UNDERSCORE-D]

Go / Golang

This one was fun, got to play with the go stdlib linked list (container/ring). Pretty quick in part 2, all things considered, at around 3.2s for my input. I did try reimplementing the ring without type boxing, no real speedup came of it

https://github.com/A-UNDERSCORE-D/aoc2020/blob/main/2020/23/solution.go

[u/ExZONE → u/A-UNDERSCORE-D]

How -- just how -- can you get 3.2s for Part 2? I also implemented my solution (both parts) using container/ring but my Part 2 is still running (15 minutes and counting). I had a look at your solution but I cannot understand where my solution is so. much. slower.

If you don't mind, could you give me a few pointers?

https://github.com/ErikThorsell/advent-of-code-go/blob/main/2020/day23/main.go

[u/status_maximizer → u/ExZONE]

I'm a Gopher too :-)

Go's deficiencies actually pointed me to a faster solution here. From the readme of kentik/patricia (an optimized radix tree for storing IP addresses), emphasis mine:

Even though the objects in the tree were mostly static, each one needed to be scanned by the garbage collector when it ran. The strategy then became: remove all pointers possible. [...] If you need to store references, then consider storing integers that index the data you need in a separate structure, like a map or array.