Advent of Code Day 9

Published December 09, 2025

It's day 9 and today's was a fun one. Part 1 was pretty easy and I had a working solution in around 20 minutes. I had a good idea of how to approach part 2 using Shapely but I had never used it before. I ended up going around in circles for a bit because of that. I eventually figured out that I was forgetting to close the polygon I was creating by including the first point at the end of the list. Once I realized that it worked like a charm.

Full solution on GitHub.!


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