Largest Product in a Series

0008/input

@@ -0,0 +1,20 @@
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0008/main.hs

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+import Data.Char (digitToInt)
+import Data.Maybe (catMaybes)
+
+findMax13 numbers =
+    foldl1 max $ map (\i -> subArrayProduct i 13) [0..((length numbers) - 13)]
+    where
+        subArrayProduct start length =
+            product $ take length (drop start numbers)
+
+main = do
+    contents <- readFile "input"
+    let max13 = findMax13 $ map digitToInt $ filter (\c -> c >= '0' && c <= '9') contents in
+        putStrLn $ show max13