参考代码:

class Solution:
    def permute(self, nums):
        def _permute(result, temp, nums):
            if nums == []:
                result += [temp]
            else:
                for i in range(len(nums)):
                    _permute(result, temp + [nums[i]], nums[:i] + nums[i + 1:])
        if nums is None:
            return []
        if nums is []:
            return [[]]
        result = []
        _permute[result, [], sorted(nums)]
        return result