Day 21: Allergen Assessment
Haskell: Part 1 (00:39:30, rank 1571), Part 2 (00:45:21, rank 1305)
This was a really easy challenge, compared to yesterday's behemoth at least. Still, as usual parsing took me quite a while. If I could get comfortable with Parsec and not make silly mistakes (like forgetting the closing ) at the end of each line), that would probably help a lot.
With part 1 solved, part 2 only took about 5 minutes since I was able to reuse the Sudoku-like map resolution code from Day 16: Ticket Translation. For a moment I suspected that backtracking might be needed, but it turned out to be solvable just by repeatedly eliminating any singleton values from all other allergen sets.