2015 Day 11 in Haskell

2015/day11/day11.hs

@@ -0,0 +1,42 @@
+import Aoc
+import Data.Char ( ord, chr )
+import Data.List ( group, nub )
+import Data.Bifunctor ( bimap )
+
+toBase26' :: Char -> Int
+toBase26' = (\n->n-97) . ord
+
+fromBase26' :: Int -> Char
+fromBase26' = chr . (97+)
+
+toBase26 :: [Char] -> [Int]
+toBase26 = reverse . map toBase26'
+
+fromBase26 :: [Int] -> [Char]
+fromBase26 = reverse . map fromBase26'
+
+next :: [Int] -> [Int]
+next (25:rest) = 0:next rest
+next (x:rest)
+    | x `elem` [7,10,13] = x+2:rest -- skip i,o,l
+    | otherwise = x+1:rest
+
+lengthy :: [a] -> Bool
+lengthy = (>1) . length
+
+getAnswer :: [[Int]] -> [Char]
+getAnswer = fromBase26 . head
+
+part1 :: String -> (String, [[Int]]) 
+part1 = (\ps -> (getAnswer ps, tail ps)) . filter isSecure . iterate next . toBase26
+    where
+        hasStraight = any lengthy . filter ((==1) . head) . group . map (uncurry (-)) . adjacents
+        hasNoIOL = not . any (`elem` [8,14,11])
+        hasPair = lengthy . nub . map head . filter lengthy . group
+        isSecure ns = hasStraight ns && hasNoIOL ns && hasPair ns
+
+part2 :: p -> [[Int]] -> String
+part2 _ = getAnswer
+
+main :: IO ()
+main = aocMain' single part1 part2