53 lines
1.6 KiB
Haskell
53 lines
1.6 KiB
Haskell
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import Data.Bits ((.&.))
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import Data.Char (ord)
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import Data.List (deleteBy, findIndex, foldl')
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import Data.List.Split (splitOn)
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import qualified Data.Vector as V
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import qualified Data.Vector.Mutable as MV
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import Data.Vector (Vector, MVector)
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type Command = (String, Maybe Int)
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getHash :: String -> Int
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getHash = foldl' (\acc x -> (acc + ord x) * 17 .&. 255) 0
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parseCommand :: String -> Command
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parseCommand s
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| last s == '-' = (init s, Nothing)
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| otherwise = (a, Just . read $ b)
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where
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(a:b:_) = splitOn "=" s
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sumFocusPower :: Vector (Vector (String, Int)) -> Int
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sumFocusPower = timesIndexAndSum . V.map (timesIndexAndSum . V.map snd)
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where
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timesIndexAndSum = V.foldl' (+) 0 . V.imap ((*) . succ)
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performCommand
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:: MVector MV.RealWorld (Vector (String, Int)) -> Command -> IO ()
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performCommand boxes (label, mFoc) = maybe performDash performEquals mFoc
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where
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boxN = getHash label
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readBox = MV.read boxes boxN
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writeBox = MV.write boxes boxN
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findPred = (== label) . fst
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performDash = writeBox . V.filter (not . findPred) =<< readBox
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performEquals foc = do
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box <- readBox
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let newLens = (label, foc)
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addNewLens = V.snoc box newLens
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swapLens i = V.modify (\v -> MV.write v i newLens) box
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writeBox . maybe addNewLens swapLens . V.findIndex findPred $ box
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main :: IO ()
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main = do
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commandStrs <- splitOn "," . concat . lines <$> readFile "data.txt"
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boxes <- MV.replicate 256 V.empty
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mapM_ (performCommand boxes . parseCommand) commandStrs
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print . sumFocusPower =<< V.unsafeFreeze boxes
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