adventofcode1614/app/advent14c.hs

   1 module Main(main) where
   2
   3 import Data.List (nub, tails)
   4 import Data.ByteString.Char8 (pack)
   5 import Crypto.Hash (hash, Digest, MD5)
   6
   7 salt = "yjdafjpo"
   8 -- salt = "abc"
   9
  10 main :: IO ()
  11 main = do
  12         part1
  13         part2
  14
  15 part1 :: IO ()
  16 part1 = print $ head $ drop 63 $ filter (\i -> possibleKey sq i && confirmKey sq i) [0..]
  17     where sq = md5sequence
  18
  19 part2 :: IO ()
  20 part2 = print $ head $ drop 63 $ filter (\i -> possibleKey sq i && confirmKey sq i) [0..]
  21     where sq = md5sequenceS
  22
  23 getHash :: String -> String
  24 getHash bs = show (hash $ pack bs :: Digest MD5)
  25
  26 md5sequence :: [String]
  27 md5sequence = [makeMd5 i | i <- [0..]]
  28     where makeMd5 i = getHash (salt ++ show i)
  29
  30 md5sequenceS :: [String]
  31 md5sequenceS = [makeMd5 i | i <- [0..]]
  32     where makeMd5 i = stretch $ getHash (salt ++ show i)
  33           stretch h0 = foldr (\_ h -> getHash h) h0 [1..2016]
  34
  35 possibleKey :: [String] -> Int-> Bool
  36 possibleKey s = not . null . repeats 3 . ((!!) s)
  37
  38 confirmKey :: [String] -> Int -> Bool
  39 confirmKey s i = any (confirmation) $ take 1000 $ drop (i+1) s
  40     where c = head $ repeats 3 $ s!!i
  41           confirmation m = c `elem` (repeats 5 m)
  42
  43 repeats :: Int -> String -> [String]
  44 repeats n = filter (null . tail) . map (nub) . substrings n
  45
  46 substrings :: Int -> [a] -> [[a]]
  47 substrings l = filter (\s -> (length s) == l) . map (take l) . tails