SUBSETS 2 DOUBT

1 
class Solution {
public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        int size = nums.size();
        vector<vector<int>>arr;
        unordered_set<string>hash_out;
        for(int i=0;i<pow(2,size);i++)
        {
            string s="";
            vector<int>temp;
            for(int j=0;j<size;j++)
            {
                if((i&(1<<j))!=0)
                {
                    s+=to_string(nums[j]);
                    temp.push_back(nums[j]);
                }
            }
            if(!hash_out.count(s))
            {
                arr.push_back(temp);
                hash_out.insert(s);
            }
        }
        return arr;
        
    }
};

My code is getting a tc wrong.