48 lines
1.4 KiB
Haskell
48 lines
1.4 KiB
Haskell
import Control.Monad (guard)
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import Data.List.Split (splitOn)
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import Data.Maybe (fromMaybe)
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import qualified Data.Vector as V
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import Data.Vector (Vector)
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nFolds :: Int
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nFolds = 5
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solve :: (Vector Int, Vector Char) -> Int
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solve (records, fences) = getAt 0 0
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where
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v = V.generate (V.length records + 1)
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$ V.generate (V.length fences + 1) . getAt'
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getAt r f = v V.! r V.! f
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getAt' r f = maybe noFencesLeft getWithFence $ fences V.!? f
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where
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noFencesLeft
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| r == V.length records = 1
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| otherwise = 0
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getWithFence thisFence = worksHere thisFence + startBreakHere
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worksHere '#' = 0
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worksHere _ = getAt r (f + 1)
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startBreakHere = fromMaybe 0
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$ do
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thisRecord <- records V.!? r
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let remainingFences = V.drop f fences
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fenceAfter <- remainingFences V.!? thisRecord
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guard $ '.' `notElem` V.take thisRecord remainingFences
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guard $ fenceAfter /= '#'
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return $ getAt (r + 1) (f + thisRecord + 1)
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parseLine :: String -> (Vector Int, Vector Char)
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parseLine l = ( unfoldRecords . map read . splitOn "," $ y
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, (`V.snoc` '.') . V.tail . unfoldRecords $ '?':x)
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where
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(x:y:_) = splitOn " " l
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unfoldRecords = V.concat . replicate nFolds . V.fromList
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main :: IO ()
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main = print . sum . map (solve . parseLine) . lines =<< readFile "data.txt"
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