I wanted to write about this day, since I thought of a nice way to solve this, which is the first time I’ve actually used this algorithm outside of class.

I’ll give a bit of a teaser: Topological Sort.

Problem

Go check out the real website, https://adventofcode.com/2024/day/5 for a full picture, but I’ll try to give as concise of a summary as possible.

Your Input

1. You are given a set of rules, like a|b, meaning number a must come before number b
2. You are given a few arrays of numbers, and
   1. For Part 1, you must sum the middle number of all arrays that conform to the above set of rules.
   2. For Part 2, you must sort the invalid arrays and find the sum of their middle numbers.

Solution

Context You are only given the first problem until you solve the second one.