12 lines
448 B
Haskell
12 lines
448 B
Haskell
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isSortedGradually :: (Integer -> Integer -> Bool) -> [Integer] -> Bool
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isSortedGradually f (x1:x2:xs) = (f x1 x2) && diff >= 1 && diff <= 3 && isSortedGradually f (x2:xs)
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where diff = abs (x1 - x2)
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isSortedGradually f _ = True
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isSafe :: [Integer] -> Bool
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isSafe xs = isSortedGradually (<) xs || isSortedGradually (>) xs
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main :: IO()
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main = interact $ show . sum . map (fromEnum . isSafe . map (read :: (String -> Integer)) . words) . lines
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