# Advent of Code 2024 **URL:** \ **Category:** Community Showcase\ **Tags:** adventofcode\ **Created:** [November 30, 2024, 11:46pm UTC](https://forums.swift.org/t/advent-of-code-2024/76301 "2024-11-30T23:46:35Z")\ **Posts on this page:** 1\ **Showing post:** 129
**Author:** ![BlueSparrow](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/bluesparrow/32/38500_2.png) [@BlueSparrow](https://forums.swift.org/u/BlueSparrow)\ **Post date:** [December 20, 2024, 9:31pm UTC](https://forums.swift.org/t/advent-of-code-2024/76301/129 "2024-12-20T21:31:37Z")
> [@gereons](#): > > One of the nice effects is that boundary detection can be done with `grid[point] == nil` instead of dealing with `0...max(X|Y)` checks. I just return a space character. I wouldn't have considered a dictionary, that's clever. I was going to ask about performance, but I don't think grid accesses are a problem with my horrible brute force solutions. * * * Speaking of 'horrible brute force solutions' doing these puzzles have given me an appreciation for how easily Swift lets me take a solution and subject all cores to my stupidity. ![Screenshot 2024-12-21 at 10.26.14](https://global.discourse-cdn.com/swift/original/3X/3/b/3bd34ce8afdcb9572fa270137d8f30650db556be.png) Main stumbling block was figuring out that this error message ![Screenshot 2024-12-21 at 10.28.37](https://global.discourse-cdn.com/swift/original/3X/0/b/0bbfd0491d7840131210d7f73e32eaaa94a39096.png) was trying to say "grid is mutable, it might change by the time this task is running". But hey, I've spent enough years writing C++ that I should be used to cryptic error messages at this point. 🙂 * * * Edit: I left the Ocean Boiler running all morning and got no results. > **Spoilers for Day 20, part 1** > > Of course, once I sat down and thought about what I was doing, I realised that you can just modify the previous graph that the Dijkstra algorithm outputs and it took 9 seconds to get the answer. --- _[View the full topic](https://forums.swift.org/t/advent-of-code-2024/76301)._