55 lines
1.8 KiB
Haskell
55 lines
1.8 KiB
Haskell
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import Data.List.Split (splitOn)
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import Data.Sequence (Seq, update, fromList)
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import qualified Data.Sequence as S (lookup)
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import Data.Char (ord)
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import Data.Bits (xor)
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import Data.Foldable (toList)
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import Numeric (showHex)
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type Ring = Seq Int
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type Position = Int
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type Skip = Int
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type Length = Int
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type State = (Ring, Position, Skip)
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(%) = mod
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unsafeLookup :: Int -> Seq Int -> Int
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unsafeLookup index seq =
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case S.lookup index seq of
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Just i -> i
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twist :: State -> Length -> State
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twist (ring, position, skip) len =
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let end = position + len - 1
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positions = map (% 256) [position..end]
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posRev = zip positions $ reverse positions
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newRing = foldl (\currRing (pos, rev) -> update pos (unsafeLookup rev ring) currRing) ring posRev
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in (newRing, (end + skip + 1) % 256, skip + 1)
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hash :: [Length] -> State -> State
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hash lengths state = foldl twist state lengths
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condense :: [Int] -> [Int]
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condense [] = []
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condense ns =
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let block = foldr xor 0 $ take 16 ns
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in block : (condense $ drop 16 ns)
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showHexPrepended :: Int -> (String -> String)
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showHexPrepended n
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| n < 15 = showHex 0 . showHex n
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| otherwise = showHex n
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main :: IO ()
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main = do
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input <- readFile "10.txt"
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let lengths = map read $ splitOn "," input
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newLengths = map ord input ++ [17, 31, 73, 47, 23]
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(hashed, _, _) = hash lengths (fromList [0..255], 0, 0)
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(sparseHash, _, _) = iterate (hash newLengths) (fromList [0..255], 0, 0) !! 64
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condensedHash = condense $ toList sparseHash
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hexString = foldr (\digit str -> showHexPrepended digit $ str) "" condensedHash
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print $ (unsafeLookup 0 hashed) * (unsafeLookup 1 hashed)
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print $ hexString
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