题目：

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代码(首刷自解 2024年2月6日）：

class Solution {
private:
    vector<vector<int>> res;
    vector<int> path;
public:
    void backtracing(vector<int>& nums, vector<bool>& used1, vector<bool>& used2) {
        if (path.size() == nums.size()) {
            res.push_back(path);
            return;
        }

        for (int i = 0; i < nums.size(); ++i) {
            if (i > 0 && nums[i] == nums[i - 1] && used1[i - 1] == true) continue;
            if (used2[i] == true) continue;
            used1[i] = true;
            used2[i] = true;
            path.push_back(nums[i]);
            backtracing(nums, used1, used2);
            path.pop_back();
            used2[i] = false;
            used1[i] = false;
        }
        return;
    }
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<bool> used1(nums.size(), 0);
        vector<bool> used2(used1);
        sort(nums.begin(), nums.end());
        backtracing(nums, used1, used2);
        return res;
    }
};