Day 21: Keypad Conundrum
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FAQ
- 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/
- Is there a leaderboard for the community?: We have a programming.dev leaderboard with the info on how to join in this post: https://programming.dev/post/6631465
Finally got this one done very late last night!
I kept getting stuck reasoning about the recursion here. For some reason I got myself convinced that after a move, the state of the ‘upper’ dpads could make it more advantageous to pick one followup move over another - i.e. steps aren’t independent.
It took a bunch of manually working through sequences to convince myself that, after every move, every dpad above it would be on A. With that, it’s ‘just’ recursive pathfinding for independent moves.
Since there are relatively few types of moves needed on the dpad, I just sketched them out and wrote the routes in code directly (up to two options per move, e.g. left,up or up,left).
Code
https://codeberg.org/sjmulder/aoc/src/branch/master/2024/c/day21.c