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Perl solutions to the Advent of Code 2019

Here are my solutions to the Advent of Code 2019, written in Perl. It was a lot of fun to figure all the solutions by myself; especially the harder ones (16.2, 18, 22, I'm looking at you!). Kudos to Eric Wastl for designing those puzzles.

I'm pretty sure that most of my solutions could be optimized: I didn't spent too much time thinking on the simple problems.

My codes are definitely not optimized for readability, and comments and fairly rare; sorry about that; I didn't plan to release them on github initially. I'll probably do better next year ;)

My codes are written as Perl module: after working on the first few problems, it seemed like it would be useful to reuse in the second part of each module functions from the first part. It also seemed that functions written in the previous days would be useful for the next ones. Well, it then turned out that not so much; having the Intcode computer as a separate module is enough... So here I am, with 50 .pm which could have been 50 .pl!

I'm especially happy with the following solutions:

  • Day 25, for which I drew a pretty map of the ship. The code itself is not particularly good, but I like the map!

  • Day 22 (part 2): I was stuck on that one for a while. I made small progresses and eventually figured it out; it was very satisfying. The code contains some explanations, but if you haven't tried it yourself, I recommend that you do!

  • Day 18: That's a funny one, because a somewhat obvious solution pops in mind quickly: Dijkstra. However, the keys make it slightly tricky, and using the grid as the graph to explore it way too expensive. I eventually figured out that I needed to compute a smaller graph, and store keys as power of 2. +1!

  • Day 16 (part 2): The last one I completed. I really had a hard time on that one. I tried to extract mathematical formulas to compute the numbers, and reduce them to something easily computable, without success... Until I figured that all factors formed a triangular matrix of 0s and 1s...


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