AOC24

my second attempt at the Advent of Code coding puzzles, 2024 edition

Some notes from this year

• First star of day 2 took a little more time than expected because I misunderstood the puzzle, I was checking the values of the neighbhour difference when it was expected to consider any list after dropping one element (which can be done simply by enumeration).
• On Day 4, for the first star I resisted the temptations to detect directly XMAS and it's reverse SAMX on a line because of the S or the X that can overlap. This has for effect that XMASAMX and SAMXMAS should each count 2 occurrence. It's possible to parametrize the regular expression to detect those overlapping matches, but I always found it tricky to do. I simply searched once on the string and one on its reverse.
• Day 5 took me too much time because I wanted to compute the transitive closure of all of the '|' relationships. It turns out that all the relationship were specified and so the problem was much more easy (and my transitive closure attempt doesn't work either -_-).
• Day 8 was really easy on the first star using an integer recoding and numpy matrices. However I got confused with matrix redimensionning and 3D matrix products on star 2 and it took me an incredible amount of time to debug. Morality: sometimes it's better to stick with the easiest solution first.
• Day 9, damn I did it too complicated for star 2, but it worked in the end
• Day 10 was so easy I did the second star on the first try without noticing
• Day 11 seemed easy and then was it took way too long for the second star. Then after thinking about it, one sees how the problem is in fact finite and the values can be indexed, it was again easy, and quite fast!