vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int> > result;
        sort(nums.begin(), nums.end());
        helper(nums, 0, result);
        return result;
    }
    void helper(vector<int> &nums, int begin, vector<vector<int> > &result) {
        if (begin == nums.size()-1) {
            result.push_back(nums);
            return;
        }

        for (int i = begin; i < nums.size(); i++) {
            if (i != begin && nums[begin] == nums[i]) continue;
            swap(nums[begin], nums[i]);
            helper(nums, begin + 1, result);
            //swap(nums[begin], nums[i]);
        }
    }
///////////////////////////
    void recursion(vector<int> num, int i, int j, vector<vector<int> > &res) {
        if (i == j-1) {
            res.push_back(num);
            return;
        }
        for (int k = i; k < j; k++) {
            if (i != k && num[i] == num[k]) continue;
            swap(num[i], num[k]);
            recursion(num, i+1, j, res);
        }
    }
    vector<vector<int> > permuteUnique__(vector<int> &num) {
        sort(num.begin(), num.end());
        vector<vector<int> >res;
        recursion(num, 0, num.size(), res);
        return res;
    }