python 代码

import copy
class Solution:

    def permutation(self, nums):

        ret = []

        flag = [False for _ in range(len(nums))]

        path = [None for _ in range(len(nums))]

        def dfs(nums, u, start):

            if u == len(nums):
                """这里如果不拷贝 那么下面进行下一次 path的排列时 会改变这个已经
                添加到 ret中的列表的结果(指向同一空间)"""
                path1 = copy.copy(path)
                ret.append(path1)
                return


            for i in range(start, len(nums)):

                if not flag[i]:
                    flag[i] = True

                    path[i] = nums[u]

                    if u + 1 < len(nums) and nums[u] != nums[u+1]:
                        dfs(nums, u+1, 0)

                    else:
                        dfs(nums, u+1, i + 1)

                    flag[i] = False

        nums.sort()
        dfs(nums, 0, 0)

        return ret