20 lines
385 B
Haskell
20 lines
385 B
Haskell
import Control.Arrow
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main :: IO ()
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main = do
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input <- parse <$> readFile "input"
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print $ day09 input
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parse :: String -> [[Int]]
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parse = map (map read . words) . lines
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day09 :: [[Int]] -> (Int, Int)
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day09 =
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(sum *** sum) .
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unzip .
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map
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((f (+) last &&& f (-) head) .
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takeWhile (not . null) . iterate (zipWith (-) =<< tail))
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where
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f f1 f2 = foldr1 f1 . map f2
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