import Data.List (nub)
import Text.ParserCombinators.ReadP

main :: IO ()
main = do
  input <- readFile "day6.in"
  putStr "Q1: "
  print $ q1 input
  putStr "Q2: "
  print $ q2 input


q1, q2 :: String -> Int
q1 = length . flip parse 4
q2 = length . flip parse 14

parse :: String -> Int -> String
parse a = parse' ("", a)

parse' :: (String, String) -> Int -> String
parse' (a, b) n
  | length (nub (drop (length a - n) a)) == n = a
  | otherwise =
    let (c, cs) = last $ readP_to_S get b
     in parse' (a ++ [c], cs) n