Day 4 done

app/4.hs

@@ -2,14 +2,43 @@
 module Main where
 
 import Data.Functor
+import Data.List
+import Data.Universe.Helpers
+import Text.Regex.PCRE
+import Data.Function
+import Debug.Trace
 
-parse = undefined
+parse1 :: String -> [String]
+parse1 a =
+  let x = lines a
+      x' = x <&> reverse in
+  x ++ -- vertical ⇒
+  x' ++ -- vertical ⇐
+  transpose x ++ -- horizontal ⇓
+  (transpose x <&> reverse) ++ -- horizontal ⇓
+  diagonals x ++ -- diagonal ⇗
+  diagonals x' ++ -- diagonal ⇖
+  (diagonals x <&> reverse) ++ -- diagonal ⇙
+  (diagonals x'<&> reverse)    -- diagonal ⇘
 
-solve1 = undefined
+solve1 :: [String] -> Int
+solve1 = sum . (length . (getAllTextMatches . (=~ "XMAS") :: String -> [String]) <$>)
 
-solve2 = undefined
+pattern2 :: Int -> String
+pattern2 i = let i' = i-2 in
+  "M.M.{"++ show i' ++"}.A..{" ++ show i' ++ "}S.S|" ++
+  "M.S.{"++ show i' ++"}.A..{" ++ show i' ++ "}M.S|" ++
+  "S.M.{"++ show i' ++"}.A..{" ++ show i' ++ "}S.M|" ++
+  "S.S.{"++ show i' ++"}.A..{" ++ show i' ++ "}M.M"
+
+solve2 :: String -> Int
+solve2 s =
+  let l = length . head . lines $ s in
+  let t = (getAllTextSubmatches . (=~ pattern2 l) :: String -> [String]) . intercalate "U" . lines <$> tails s
+      t' = nub . concat $ t in
+    length t'
 
 main :: IO ()
-main = readFile "inputs/4" <&> parse >>= \i ->
-       print (solve1 i) >>
+main = readFile "inputs/4" >>= \i ->
+       print (solve1 $ parse1 i) >>
        print (solve2 i)