Advent of Code 2023 - Day 21

Learning Resources Coding Challenges
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2

I am finally unstuck. :smile:

I managed to solve the problem without any hints from Reddit. I did use WolframAlpha for helping me find the formulas for the sum of some sequences.

My solution is not a general solution. I’ve hard-coded magic numbers specific for my input. I didn’t bother writing a more general solution that would calculate those magic numbers using the code for part 1.

There are some brief comments in the code that gives some hints of how I solved it. I’ve also kept some of the debug code I used for understanding the input.

https://github.com/bjorng/advent-of-code-2023/blob/main/day21/lib/day21.ex