SubsetII.cpp

 class Solution {
public:
    vector<vector<int> > subsetsWithDup(vector<int> &S) {
        vector<vector<int> > totalset = {{}};
        sort(S.begin(),S.end());
        for(int i=0; i<S.size();){
            int count = 0; // num of elements are the same
            while(count + i<S.size() && S[count+i]==S[i])  count++;
            int previousN = totalset.size();
            for(int k=0; k<previousN; k++){
                vector<int> instance = totalset[k];
                for(int j=0; j<count; j++){
                    instance.push_back(S[i]);
                    totalset.push_back(instance);
                }
            }
            i += count;
        }
        return totalset;
        }
}