aoc/app/1.hs

{-# LANGUAGE LambdaCase #-}
{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
{-# HLINT ignore "Redundant <&>" #-}
module Main where

import Data.Functor
import Data.List.Split
import Data.Char
import Data.Function
import Data.List

parse :: String -> ([Int], [Int])
parse = unzip .
  ((\case
      [a,b] -> (read a, read b)
      e -> error $ "Parsing failed on: " ++ show e
      ) <$>) .
  (filter (/= mempty) . splitWhen isSpace <$>)  .
  lines

solve1 :: ([Int], [Int]) -> Int
solve1 = sum . uncurry (zipWith ((abs .) . (-)) `on` sort)

solve2 ::  ([Int], [Int]) -> Int
solve2 (as,bs) = foldr (\a -> (a * length (filter (==a) bs) +)) 0 as

main :: IO ()
main = readFile "inputs/1" <&> parse >>= \i ->
       print (solve1 i) >>
       print (solve2 i)