advent-of-code-2022/src/Day3/Part1.hs

module Day3.Part1 (
  splitContents,
  itemsInBoth,
  itemPriority,
  priority,
  rearrangementPriority,
)
where

import qualified Data.Set as Set
import Day3.Shared


splitContents :: Contents -> (Contents, Contents)
splitContents c = splitAt middle c
  where
    middle = length c `div` 2

itemsInBoth :: Contents -> Contents
itemsInBoth cs = Set.toList $ leftSet `Set.intersection` rightSet
  where
    (left, right) = splitContents cs
    leftSet = Set.fromList left
    rightSet = Set.fromList right

rearrangementPriority :: String -> Int
rearrangementPriority input = sum priorities
  where
    contents = lines input
    priorities = map (priority . itemsInBoth) contents