module Main (main) where

import Data.List (sort)

-- | Part 1
extractLists :: String -> ([Int], [Int])
extractLists = unzip . map ((\[a, b] -> (read a :: Int, read b :: Int)) . words) . lines

calculateDifferences :: ([Int], [Int]) -> [Int]
calculateDifferences (a, b) = zipWith (\n1 n2 -> abs (n1 - n2)) (sort a) (sort b)

part1 :: String -> IO ()
part1 = print . sum . calculateDifferences . extractLists

-- | Part 2
countIn :: [Int] -> Int -> Int
countIn [] _ = 0
countIn (x : xs) n
  | n == x = 1 + countIn xs n
  | otherwise = countIn xs n

similarityScore :: [Int] -> Int -> Int
similarityScore l n = n * countIn l n

part2 :: String -> IO ()
part2 = print . sum . (\(a, b) -> map (similarityScore b) a) . extractLists

-- | Main
main :: IO ()
main = readFile "resources/day1.txt" >>= part2