adventofcode1614/app/advent14.hs

   1 module Main(main) where
   2
   3 import Data.List (nub, tails, null)
   4 import Data.Hash.MD5 (md5s, Str(..))
   5
   6 salt = "yjdafjpo"
   7 -- salt = "abc"
   8
   9 main :: IO ()
  10 main = do
  11         part1
  12         part2
  13
  14 part1 :: IO ()
  15 part1 = print $ head $ drop 63 $ filter (\i -> possibleKey sq i && confirmKey sq i) [0..]
  16     where sq = md5sequence
  17
  18 part2 :: IO ()
  19 part2 = print $ head $ drop 63 $ filter (\i -> possibleKey sq i && confirmKey sq i) [0..]
  20     where sq = md5sequenceS
  21
  22 md5sequence :: [String]
  23 md5sequence = [makeMd5 i | i <- [0..]]
  24     where makeMd5 i = md5s (Str (salt ++ show i))
  25
  26 md5sequenceS :: [String]
  27 md5sequenceS = [makeMd5 i | i <- [0..]]
  28     where makeMd5 i = stretch $ md5s (Str (salt ++ show i))
  29           stretch h0 = foldr (\_ h -> md5s (Str h)) h0 [1..2016]
  30
  31 possibleKey :: [String] -> Int-> Bool
  32 possibleKey s = not . null . repeats 3 . ((!!) s)
  33
  34 confirmKey :: [String] -> Int -> Bool
  35 confirmKey s i = any (confirmation) $ take 1000 $ drop (i+1) s
  36     where c = head $ repeats 3 $ s!!i
  37           confirmation m = c `elem` (repeats 5 m)
  38
  39 repeats :: Int -> String -> [String]
  40 repeats n = filter (null . tail) . map (nub) . substrings n
  41
  42 substrings :: Int -> [a] -> [[a]]
  43 substrings l = filter (\s -> (length s) == l) . map (take l) . tails