Advent Of Code

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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 2024

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👻 - 2024 DAY 19 SOLUTIONS -👻 (programming.dev)

submitted 6 days ago by [email protected] to c/[email protected]

31 comments fedilink hide all child comments

Day 19 - Linen Layout

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[–] [email protected] 2 points 6 days ago* (last edited 6 days ago) (1 children)

That does mean that if two or more strings end with the same substring, you'd recalculate those substrings? Would be a faster lookup cost though, clever.

My code ran in 120ms, so its pretty damn fast as is, especially compared to the non-memoised version

edit: Tried the array of lengths method, shaved about 20ms off. Not bad, but probably not my main issue either

[–] [email protected] 3 points 6 days ago (1 children)

That does mean that if two or more strings end with the same substring, you’d recalculate those substrings?

I hadn't really considered that, but yes. I'm inclined to think that replacing hash table lookups with plain array indexing (which this allows) outweighs that downside but I'm not sure. Indeed 120ms is pretty damn fast!

[–] [email protected] 1 points 6 days ago (1 children)

It saved me 20ms, and given your using C, saved you dealing with uthash or similar, so probably worth it.

The hashmap is probably a more generic solution though

[–] [email protected] 2 points 6 days ago

Certainly more generic and less prone to user error too. Indeed dealing with hash maps or any advanced data structure is a pain with C, this is where generics or templates really shine, especially if you have control over lifetime aspects as you do with C++ or Rust (e.g. moves, lvalue references, constness, etc).