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 2024

Solution Threads

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16	17	18	18	20	21	22
23	24	25

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Keep all content related to advent of code in some way
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console.log('Hello World')

founded 1 year ago

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Ategon

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CameronDev

🎄 - 2023 DAY 15 SOLUTIONS -🎄 (self.advent_of_code)

submitted 11 months ago* (last edited 11 months ago) by Ategon to c/advent_of_code

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Day 15: Lens Library

Megathread guidelines

Keep top level comments as only solutions, if you want to say something other than a solution put it in a new post. (replies to comments can be whatever)
Code block support is not fully rolled out yet but likely will be in the middle of the event. Try to share solutions as both code blocks and using something such as https://topaz.github.io/paste/ , pastebin, or github (code blocks to future proof it for when 0.19 comes out and since code blocks currently function in some apps and some instances as well if they are running a 0.19 beta)

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What is this?: Here is a post with a large amount of details: https://programming.dev/post/6637268
Where do I participate?: https://adventofcode.com/
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[–] [email protected] 5 points 11 months ago (1 children)

Rust

Part 1 was super simple with wrapping_add and wrapping_mul on a u8. Building an actual hash map in Part 2 was nice.

[–] [email protected] 2 points 11 months ago (1 children)

That array initialisation is pure poetry! 😄

[–] [email protected] 2 points 11 months ago (1 children)

I'm not fluent in Rust, but is this something like the C++ placement new? Presumably just declaring a table of Vecs won't automatically call the default constructor? (Sorry for my total ignorance -- pointers to appropriate reading material appreciated)

[–] [email protected] 1 points 11 months ago (1 children)

You can create an array filled with all the same values in Rust, but only if all values have the same memory representation because they will be copied. That just doesn't work with Vec's, because they must all have their own unique pointer. And to have uninitialized values at first (think NULL-pointers for every Vec) while creating each Vec, something like this is apparently needed.

The appropriate way would certainly have been to store the map as a Vec> instead of an array, but I just wanted to see if could.

[–] [email protected] 1 points 11 months ago

Ah, I see! Thank you.