aoc/app/9.hs

{-# LANGUAGE LambdaCase #-}
module Main where

import Data.Functor
import Data.List
import Data.List.Extra

data ℜ where
  None :: ℜ
  Num  :: Int -> ℜ
    deriving Eq

instance Show ℜ where
  show None = show '.'
  show (Num n) = show n

parse :: String -> [ℜ]
parse s = zip [0..] (trim s) >>= \(i,a) -> replicate (read [a]) (if even i then Num (i `div` 2) else None)

sort1 :: [ℜ] -> [ℜ]
sort1 s
  | None `notElem` s = s
  | otherwise = case last s of
                  None -> sort1 $ init s
                  n    -> sort1 $ takeWhile (/= None) s ++ [n] ++ drop 1 (dropWhile (/= None) (init s))

sort2 :: [ℜ] -> [ℜ]
sort2 = undefined

solve :: ([ℜ] -> [ℜ]) -> [ℜ] -> Int
solve f s = let fixed = (\(Num n) -> n) <$> f s in
  sum $ zipWith (*) fixed [0..]

main :: IO ()
main = readFile "inputs/9.example" <&> parse >>= \i ->
       print (solve sort1 i) >>
       print (solve sort2 i)