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21 lines
599 B
Haskell
21 lines
599 B
Haskell
splitWhen :: (a -> Bool) -> [a] -> ([a], [a])
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splitWhen _ [] = ([], [])
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splitWhen p (x:xs)
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| p x = ([], x:xs)
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| otherwise = let (ys, zs) = splitWhen p xs
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in (x:ys, zs)
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-- >>> splitWhen even [1,2,3]
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-- ([1],[2,3])
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group :: Eq a => [a] -> [[a]]
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group [] = []
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group (x:xs) = let (group1, rest) = splitWhen (/=x) xs
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in (x:group1) : group rest
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encode :: Eq a => [a] -> [(a, Int)]
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encode xs = map (\x -> (head x, length x)) (group xs)
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decode [] = []
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decode ((x,n):xs) = replicate n x ++ decode xs
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-- alternativ
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decode = concat . (map (\(x,n)->replicate n x))
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