6 lines
249 B
Haskell
6 lines
249 B
Haskell
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permutations :: [a] -> [[a]]
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permutations = foldr (concatMap . insertEverywhere) [[]]
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where insertEverywhere :: a -> [a] -> [[a]]
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insertEverywhere x [] = [[x]]
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insertEverywhere x l@(y:ys) = (x:l) : map (y:) (insertEverywhere x ys)
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