tvl-depot/users/wpcarro/scratch/facebook/recursion-and-dynamic-programming/permutations.py

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def char_and_rest(i, xs):
return xs[i], xs[:i] + xs[i+1:]
# perms :: String -> [String]
def perms(xs):
if len(xs) == 1:
return [xs]
result = []
for c, rest in [char_and_rest(i, xs) for i in range(len(xs))]:
result += [c + perm for perm in perms(rest)]
return result
print(perms("cat"))