24 lines
883 B
Haskell
24 lines
883 B
Haskell
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import Control.Applicative (empty)
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import Control.Monad.Zip (mzip)
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import Data.List (intercalate)
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import Data.Maybe (catMaybes)
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compose2 :: (a' -> b' -> c) -> (a -> a') -> (b -> b') -> a -> b -> c
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compose2 f g h x y = f (g x) (h y)
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(.:) :: (c -> d) -> (a -> b -> c) -> a -> b -> d
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f .: g = (f .) . g
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infixl 8 .:
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countHits :: (Int, Int) -> [[Bool]] -> Int
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countHits = length . filter id . map (uncurry $ flip (!!)) . catMaybes .: compose2 (zipWith mzip) (uncurry . flip $ compose2 intercalate (flip replicate empty . pred) (fmap pure . map pure . enumFromThen 0)) (map pure)
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treeCharToBool :: Char -> Bool
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treeCharToBool = (== '#')
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main = do
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charLines <- lines <$> readFile "input.txt"
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let boolLines = cycle <$> map treeCharToBool <$> charLines
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print $ countHits (3, 1) boolLines
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print $ product $ flip countHits boolLines <$> [(1,1), (3,1), (5,1), (7,1), (1,2)]
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