2015 Day 04 in Haskell

2015/day04/day04.hs

@@ -0,0 +1,23 @@
+import Aoc
+import Crypto.Hash.MD5 ( hash )
+import Data.ByteString.Char8 ( pack )
+import Data.ByteString.Builder ( byteStringHex, toLazyByteString )
+import Data.ByteString.Lazy.Char8 ( pack, isPrefixOf )
+
+parseFile :: [String] -> [Char]
+parseFile = single
+
+mine :: Int -> [Char] -> Int
+mine n key = head $ filter matches [1..]
+    where
+        zeros = Data.ByteString.Lazy.Char8.pack $ replicate n '0'
+        matches = isPrefixOf zeros . toLazyByteString . byteStringHex . hash . Data.ByteString.Char8.pack . (key++) . show
+
+part1 :: [Char] -> Int
+part1 = mine 5
+
+part2 :: [Char] -> Int
+part2 = mine 6
+
+main :: IO ()
+main = aocMain parseFile part1 part2

aoc.hs

@@ -4,9 +4,9 @@ aocMain :: Show p => ([String] -> p) -> (p -> Int) -> (p -> Int) -> IO ()
 aocMain parseFile part1 part2 = do
     contents <- readFile "input.txt"
     let input = parseFile $ lines contents
-    -- print $ "Input: " ++ show input
+    -- putStrLn $ "Input: " ++ show input
-    print $ "Part 1: " ++ show (part1 input)
+    putStrLn $ "Part 1: " ++ show (part1 input)
-    print $ "Part 2: " ++ show (part2 input)
+    putStrLn $ "Part 2: " ++ show (part2 input)
 
 enumerate :: [a] -> [(Int, a)]
 enumerate xs = zip [0..length xs] xs