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benjamin-hodgson/Permutations.hs

Last active May 25, 2018 14:10
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Permutations.hs
permutations :: [a] -> [[a]]
permutations [] = [[]]
permutations (x:xs) = concatMap (insertions x) (permutations xs)
where
insertions x [] = [[x]]
insertions x zs@(y:ys) = (x:zs) : [y:ins | ins <- insertions x ys]
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