aoc/app/11.hs

{-# LANGUAGE LambdaCase #-}
module Main where

import Data.Functor
import Data.List.Split

parse :: String -> [Int]
parse = (read <$>) . words

rules :: [(Int -> Bool, Int -> [Int])]
rules =
  [
   ((==0), const [1])
  ,(even . length . show, \a -> let b = show a; s = length b in chunksOf (s `div` 2) b <&> read)
  ,(const otherwise, pure . (*2024))
  ]

applyRule :: Int -> [Int]
applyRule i = head . filter (/= mempty) $ rules >>= \(f,g) -> if f i then pure $ g i else pure mempty

step :: [Int] -> [Int]
step = (applyRule =<<)

applyAmount :: Int -> a -> (a -> a) -> a
applyAmount 0 a _ = a
applyAmount n a f = f $ applyAmount (n-1) a f

solve1 :: [Int] -> Int
solve1 = length . flip (applyAmount 25) step

solve2 :: [Int] -> Int
solve2 = undefined

main :: IO ()
main = readFile "inputs/11" <&> parse >>= \i ->
       print (solve1 i) >>
       print (solve2 i)