class Solution {
public:
    vector<int> part;
    vector<vector<int>> res;
    vector<vector<int>> permutation(vector<int>& nums) {
        part.resize(nums.size());
        sort(nums.begin(), nums.end());
        dfs(nums, 0, 0, 0);
        return res;
    }
    void dfs(vector<int>& nums, int u, int start, int state){
        if(u == nums.size()){
            res.push_back(part);
            return ;
        }
        if(!u || nums[u] != nums[u - 1])    start = 0;
        for(int i = start; i < nums.size(); i ++ ){
            if(!(state >> i & 1)){
                part[i] = nums[u];
                dfs(nums, u + 1, i + 1, state | (1 << i));
            }
        }
    }
};