21 lines
609 B
Haskell
21 lines
609 B
Haskell
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import Debug.Trace
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debug = flip trace
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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 (x1:_) = True
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isSortedGradually f _ = True
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isAscending :: [Integer] -> Bool
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isAscending = isSortedGradually (<)
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isDescending :: [Integer] -> Bool
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isDescending = isSortedGradually (>)
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ok xs = isAscending xs || isDescending xs
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main :: IO()
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main = interact $ show . sum . map (fromEnum . ok . map (read :: (String -> Integer)) . words) . lines
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