day6

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

day6.hs

@@ -0,0 +1,25 @@
+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