-- https://adventofcode.com/2024/day/1

import           Data.List
import           GHC.IO

input :: FilePath
input = "src/advent_of_code/2024/1.input"

entries :: ([Int], [Int])
entries = unzip $ map parse' $ unsafePerformIO $ lines <$> readFile input

main :: IO ()
main = do
  entries <- lines <$> readFile input
  print "Advent of Code 2024 - Day 1"

  print $ "Part 1: " <> show (solveP1 $ unzip $ map parse' entries)
  print $ "Part 2: " <> show (solveP2 $ unzip $ map parse' entries)

parse' :: String -> (Int, Int)
parse' str = (read l, read r)
  where
    l = take' str
    r = reverse $ take' $ reverse str
    take' = takeWhile (/= ' ')

solveP1 :: ([Int], [Int]) -> Int
solveP1 (as, bs) = sum $ zipWith (\i j -> abs (i - j)) as' bs'
  where
    as' = sort as
    bs' = sort bs

solveP2 :: ([Int], [Int]) -> Int
solveP2 (as, bs) = sum $ zipWith (*) as (map (f bs) as)
  where
    f :: [Int] -> Int -> Int
    f bs a = length $ elemIndices a bs