X-Git-Url: https://git.njae.me.uk/?a=blobdiff_plain;f=advent05.hs;fp=advent05.hs;h=d86bd5aee32ee5301f82a3dc099b2e4eafcc604d;hb=fef438e522205404e0e765414e412ccacc34bfaa;hp=0000000000000000000000000000000000000000;hpb=f7a6219e119fedd3abd3d6967f1c6d104b04d8e4;p=advent-of-code-16.git

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+module Main(main) where
+
+import Data.Hash.MD5 (md5s, Str(..))
+import Data.List (isPrefixOf)
+import qualified Data.Map.Lazy as Map 
+
+type Password = Map.Map Integer Char
+
+input = "cxdnnyjw"
+
+main :: IO ()
+main = do 
+        part1 
+        part2
+
+
+part1 :: IO ()
+part1 = do 
+    print $ take 8 [h!!5 | h <- filter (interesting) $ md5sequence input 0]
+
+part2 :: IO ()
+part2 = do 
+    print $ Map.foldr (:) [] password
+    where interestingHashes = 
+            [(read [h!!5], h!!6) | 
+              h <- filter (interesting) (md5sequence input 0), 
+              h!!5 `elem` "01234567"]
+          password = findPassword Map.empty interestingHashes
+
+
+md5sequence :: String -> Integer -> [String]
+md5sequence key i = (md5s (Str (key ++ show i))) : (md5sequence key (i+1))
+
+interesting :: String -> Bool
+interesting hash = "00000" `isPrefixOf` hash
+
+dontReplace :: (Integer, Char) -> Password -> Password
+dontReplace (k, v) = Map.insertWith (\_ v -> v) k v
+
+findPassword :: Password -> [(Integer, Char)] -> Password
+findPassword p (candidate:candidates)
+  | Map.size p == 8 = p
+  | otherwise = findPassword p' candidates
+      where p' = dontReplace candidate p