38 lines
1.2 KiB
Haskell
38 lines
1.2 KiB
Haskell
import Data.Foldable (toList)
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import Data.Maybe
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import Data.HashMap (Map, member, insert, findWithDefault, empty)
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import Data.Sequence (Seq, update, fromList, elemIndexL, mapWithIndex)
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import qualified Data.Sequence as S (length)
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type Bank = Seq Int
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type Config = (Bank, Map [Int] Int)
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(%) = mod
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(//) = div
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getMaxMem :: Bank -> (Int, Int)
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getMaxMem bank =
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(fromJust $ elemIndexL (maximum bank) bank, maximum bank)
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nextBank :: Bank -> Bank
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nextBank bank =
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let len = S.length bank
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(index, value) = getMaxMem bank
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newBank = fmap (+ value // len) $ update index 0 bank
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indices = fmap (% len) [index + 1..index + value % len]
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in mapWithIndex (\i v -> v + fromEnum (i `elem` indices)) newBank
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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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bank <- fmap (fromList . map read . words) $ readFile "6.txt"
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print $ cycles 0 (bank, empty)
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