47. 全排列 II

class Solution {
public:
vector> vec_vec_int;
    vector> permuteUnique(vector& nums) {
        sort(nums.begin(),nums.end());
        backtrack(nums, 0);
        return vec_vec_int;
    }
    void backtrack(vector nums, int level){
        vector vec_int;
        if(level == nums.size() - 1){
            vec_vec_int.push_back(nums);
            return;
        }
        for(int i = level; i < nums.size(); i++){
            if(i != level && nums[i] == nums[level])
                continue;
            swap(nums[i], nums[level]);
            backtrack(nums, level + 1);
        }
    }
};