打卡题目：leetcode第47题，全排列Ⅱ
    相似题目：46
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    【代码】

    1. class Solution:
    2.     def permuteUnique(self, nums: List[int]) -> List[List[int]]:
    3.         def dfs(nums, size, depth, path, used, res):
    4.             if depth == size:
    5.                 res.append(path.copy())
    6.                 return
    7.             for i in range(size):
    8.                 if not used[i]:
    9.                     if i > 0 and nums[i] == nums[i-1] and not used[i-1]:
    10.                         continue
    11.                     used[i] = True
    12.                     path.append(nums[i])
    13.                     dfs(nums, size, depth+1, path, used, res)
    14.                     used[i] = False
    15.                     path.pop()
    16.         size = len(nums)
    17.         if size == 0:
    18.             return []
    20.         nums.sort()
    22.         used = [False] * len(nums)
    23.         res = []
    24.         dfs(nums, size, 0, [], used, res)
    25.         return res