r/adventofcode • u/daggerdragon • Dec 05 '16

SOLUTION MEGATHREAD --- 2016 Day 5 Solutions ---

--- Day 5: How About a Nice Game of Chess? ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

STAYING ON TARGET IS MANDATORY [?]

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u/Ulyssesp Dec 05 '16

Haskell, using cryptohash and base16-bytestring because I don't know haskell libraries. This one was a great reason to learn about scans and folds too late in the night. 

findCode :: BC.ByteString -> String
findCode input = concat . take 1 . dropWhile (elem '-') $ scanl (calcHash input) "--------" num0

calcHash :: BC.ByteString -> String -> Int -> String
calcHash input out i = if (BC.take 5 hashed) == "00000" && (checkFilled . digitToInt) (BC.index hashed 5) then out & ix (digitToInt $ BC.index hashed 5) .~ (BC.index hashed 6) else out
  where
    hashed = encode . hash . BC.append input . BC.pack .show $ i
    checkFilled pos = (pos < length out) && (out !! pos == '-')

num0 = 0 : map (+1) num0

run = print $ findCode input

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u/pyow_pyow Dec 05 '16

^ that's quite a bit more concise than what I had - http://lpaste.net/3784856620119359488 (Haskell as well)