gerikson

urgh this took me much longer than it should have... part 1 was easy enough but then I got tied up in knots with part 2. Finally I just sorto-bogo-sorted it all into shape

Perl: https://github.com/gustafe/aoc2024/blob/main/d05-Print-Queue.pl

Recheck array size: 98
All rechecks passed after 5938 passes
Duration: 00h00m00s (634.007 ms)

is it really n^2 tho? You have to do a constant check around each element, but that does not increase with the number of elements. And you can optimize a bit by marking already seen 'A's as illegal states and don't have to check them when the next row is processed.

There's probably a smarter way to do this...

For part 1, I dumped everything into a matrix. Then I scanned it element by element. If I found an X, I searched in 8 directions from there and counted up if I found M A S in sequence.

For part 2 I searched for an A, checked each diagonal corner, and counted up if the opposites were M S or S M

https://github.com/gustafe/aoc2024/blob/main/d04-Ceres-Search.pl

I expect much wailing and gnashing of teeth regarding the parsing, which of course is utterly trivial if you know a bit if regex.

I got bit by the input being more than one line. Embarrasing.

I wonder if any input starts with a "don't()" or if it's too early for Erik to pull such trickery.

I was convinced that some of the Perl gods in the subreddit would reveal some forgotten lore that solved this in one line but looks like my brute force method of removing one element at a time was the way to go.