43 lines
1.4 KiB
Haskell
43 lines
1.4 KiB
Haskell
import Data.Foldable (toList)
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import Data.HashMap (Map, member, insert, findWithDefault, empty)
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import Data.Sequence (Seq, length, update, fromList, foldlWithIndex, mapWithIndex)
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type Bank = Seq Int
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type HashableBank = [Int]
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type Config = (Bank, Map HashableBank Int)
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(%) :: Int -> Int -> Int
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(%) = mod
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(//) :: Int -> Int -> Int
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(//) = div
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getMaxMem :: Bank -> (Int, Int)
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getMaxMem bank =
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foldlWithIndex (\(currIndex, currMax) index value -> if value > currMax then (index, value) else (currIndex, currMax)) (0, 0) bank
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nextBank :: Bank -> Bank
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nextBank bank =
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let len = Data.Sequence.length bank
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(index, value) = getMaxMem bank
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zeroedBank = update index 0 bank
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mappedBank = fmap (+ value // len) zeroedBank
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indicesToUpdate = fmap ((% len) . (+ index)) [1..value % len]
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in mapWithIndex (\i v -> if i `elem` indicesToUpdate then v + 1 else v) mappedBank
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cycles :: Int -> Config -> (Int, Int)
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cycles prevCount (prevBank, banks) =
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let count = prevCount + 1
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bank = nextBank prevBank
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hashableBank = toList bank
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in if member hashableBank banks
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then (count, count - findWithDefault undefined hashableBank banks)
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else cycles count (bank, insert hashableBank count banks)
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main :: IO ()
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main = do
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input <- readFile "6.txt"
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let bank = fromList $ fmap read $ words input :: Bank
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print $ cycles 0 (bank, empty)
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