AoC2018/Day5/Part1.hs

19 lines
499 B
Haskell
Executable File

#! /usr/bin/env stack
-- stack --resolver lts-12.20 --install-ghc script
{-# LANGUAGE ViewPatterns #-}
module Main where
import qualified Data.Char as C
import qualified Data.List as L
main :: IO ()
main = interact $ show . length . react . takeWhile C.isAlpha
react [] = []
react (x:(react -> ys))
| (y:ys') <- ys, x `reactsWith` y = ys'
| otherwise = x:ys
x `reactsWith` y = (C.isUpper x && C.toLower x == y) ||
(C.isLower x && C.toUpper x == y)