day03.md

Some more "string" processing! First, let's assume that we receive a list of priority sequences instead of a list of character strings. Both of these parts are actually the same problem, the only difference is how we get our groups. Once we get the groups, we can convert each string into an IntSet and find the mutual intersection between all of the groups with IS.intersection and foldl1:

import qualified Data.IntSet as IS

solve :: [[Int]] -> Int
solve = sum . map go
  where
    getPriority = IS.findMin . foldl1 IS.intersection . map IS.fromList

Then each part is just finding the right splitting function:

part1, part2 :: [Int] -> Int
part1 = solve . map (\xs -> chunksOf (length xs `div` 2) xs)
part2 = solve . chunksOf 3