From 4f70d5ef99ffcbeee55ccffdb3464a9bb947f3ab Mon Sep 17 00:00:00 2001
From: Neil Smith <neil.git@njae.me.uk>
Date: Sat, 17 Dec 2016 10:48:17 +0000
Subject: [PATCH] Parallel version, but consumes vast amounts of resources

---
 advent14parallel.hs | 48 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 advent14parallel.hs

diff --git a/advent14parallel.hs b/advent14parallel.hs
new file mode 100644
index 0000000..cb3e1b6
--- /dev/null
+++ b/advent14parallel.hs
@@ -0,0 +1,48 @@
+import Data.List (nub, tails)
+import Data.ByteString.Char8 (pack)
+import Crypto.Hash (hash, Digest, MD5)
+import Control.Parallel.Strategies (parMap, rdeepseq)
+
+salt = "yjdafjpo"
+-- salt = "abc"
+
+main :: IO ()
+main = do 
+        part1 
+        part2
+
+part1 :: IO ()
+part1 = print $ head $ drop 63 $ filter (\i -> possibleKey sq i && confirmKey sq i) [0..]
+    where sq = md5sequence
+
+part2 :: IO ()
+part2 = print $ head $ drop 63 $ filter (\i -> possibleKey sq i && confirmKey sq i) [0..]
+    where sq = md5sequenceS
+
+getHash :: String -> String
+getHash bs = show (hash $ pack bs :: Digest MD5)
+
+md5sequence :: [String]
+-- md5sequence = [makeMd5 i | i <- [0..]]
+md5sequence = parMap rdeepseq (makeMd5) [0..]
+    where makeMd5 i = getHash (salt ++ show i)
+
+md5sequenceS :: [String]
+-- md5sequenceS = [makeMd5 i | i <- [0..]]
+md5sequenceS = parMap rdeepseq (makeMd5) [0..]
+    where makeMd5 i = stretch $ getHash (salt ++ show i)
+          stretch h0 = foldr (\_ h -> getHash h) h0 [1..2016]
+
+possibleKey :: [String] -> Int-> Bool
+possibleKey s = not . null . repeats 3 . ((!!) s)
+
+confirmKey :: [String] -> Int -> Bool
+confirmKey s i = any (confirmation) $ take 1000 $ drop (i+1) s
+    where c = head $ repeats 3 $ s!!i
+          confirmation m = c `elem` (repeats 5 m)
+                              
+repeats :: Int -> String -> [String]
+repeats n = filter (null . tail) . map (nub) . substrings n
+
+substrings :: Int -> [a] -> [[a]]
+substrings l = filter (\s -> (length s) == l) . map (take l) . tails
-- 
2.34.1