Day 8: Seven Segment Search
Haskell: Part 1 (00:21:38, rank 6191), Part 2 (01:44:13, rank 5065)
Another cool puzzle, this time involving a jumbled 7-segment display we had to decode. Reminiscent of the monster jigsaw puzzle from last year but not quite as mindmelting.
This part was pretty easy but I got stuck in parsing for a while.
Here's where it got really interesting. I think there were clever ways of doing this with constraint programming (probably a good use for Picat), but I chose the brute force approach and just generated all 5040 permutations of the letters abcdefg, then checked each code in the current input line against a template for each character to see if there was a match. I used sets for the matching since indices [2,5] produce the same digit as [5,2].
This took me a really long time, and I got stuck at some point trying to lift [Just a] up to [a], before discovering catMaybes in the Data.Maybe package. Another problem where it might be beneficial to sketch the solution out on paper before proceeding, although whenever I do that, the initial sketch is invalidated quite quickly...