The idea is to make sure that every tmp.push_back(S[i]) can make a new subset, and then push it in the res.

```
void helper(vector<int> tmp,vector<vector<int>> &res,vector<int> &S, int start){
res.push_back(tmp);
int n=S.size();
for(int i=start;i<n;i++){
if(i>start&&S[i]==S[i-1])continue;//skip the duplicate element
tmp.push_back(S[i]);
helper(tmp,res,S,i+1);
tmp.pop_back();
}
}
vector<vector<int> > subsetsWithDup(vector<int> &S) {
vector<vector<int>> res;
vector<int> tmp;
sort(S.begin(),S.end());
helper(tmp,res,S,0);
return res;
}`
```