Add day 4

4.hs

@@ -0,0 +1,28 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+import Data.Char
+import Data.List.Split
+import Data.List
+import Data.Maybe
+
+main = do
+    ls <- readFile "4.in"
+    putStrLn . show . solveB . parse$ ls
+    where
+        solveA :: [[[Int]]] -> Int
+        solveA = length . filter id . map contains
+
+        solveB :: [[[Int]]] -> Int
+        solveB = length . filter id . map overlaps
+
+        parse :: String -> [[[Int]]]
+        parse = map ( map (map parseInt . splitOn "-") . splitOn ",") .lines where
+            parseInt = read :: String -> Int
+        
+        contains :: Ord a => [[a]] -> Bool
+        contains [[a,b],[c,d]] = isSorted [a, c, d, b] || isSorted [c, a, b, d]
+
+        overlaps :: Ord a => [[a]] -> Bool
+        overlaps [[a,b],[c,d]] = isSorted [a,c,b] || isSorted [a,d,b] || isSorted [c, a, d] || isSorted [c, b, d]
+
+        isSorted :: Ord a => [a] -> Bool
+        isSorted x = x == sort x