26 lines
881 B
Haskell
26 lines
881 B
Haskell
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import Data.Vector.Unboxed (Vector, fromList, (!), (//))
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import qualified Data.Vector.Unboxed as V (length)
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type Length = Int
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type Index = Int
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type Steps = Int
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type State = (Steps, Index, Vector Int)
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type Update = Int -> Int
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next :: Update -> State -> State
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next f (steps, i, jumps) =
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let value = jumps ! i
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nextI = i + value
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nextJumps = jumps // [(i, f value)]
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in (steps + 1, nextI, nextJumps)
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getExitSteps :: Update -> State -> Int
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getExitSteps f (steps, i, jumps) =
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if i >= V.length jumps then steps else getExitSteps f $! next f (steps, i, jumps)
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main :: IO ()
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main = do
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input <- readFile "5.txt"
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let jumpsList = fromList $ map read $ lines input
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print $ getExitSteps (+1) (0, 0, jumpsList)
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print $ getExitSteps (\v -> if v >= 3 then v - 1 else v + 1) (0, 0, jumpsList)
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