Subsets II

Given a collection of integers that might contain duplicates, S, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If S = [1,2,2], a solution is:

[ [2], [1], [1,2,2], [2,2], [1,2], [] ]

class  Solution {
public:
    vector<vector< int> > subsetsWithDup(vector< int> &S) 
    {
        vector< int> keys;
        vector< int> count;
         // count pairs
         for( int i= 0;i<S.size();i++)
        {
             int j= 0;
             for(j= 0;j<keys.size();j++)
                 if(keys[j]==S[i])  break;
             if(j==keys.size()) 
            {
                keys.push_back(S[i]);
                count.push_back( 1);
            }
             else
            {
                count[j]++;
            }
        }
         // sort pairs
         for( int i= 0;i<keys.size();i++)
             for( int j=i+ 1;j<keys.size();j++)
             if(keys[i]>keys[j])
            {
                 int tmp=keys[i];
                keys[i]=keys[j];
                keys[j]=tmp;
                tmp=count[i];
                count[i]=count[j];
                count[j]=tmp;
            }
            
        vector< int> v;
         for( int i= 0;i<keys.size();i++) v.push_back( 0);
        
        vector<vector< int>> result;
        generate(result,keys,count,v, 0);
         return result;
    }
    
     void generate(vector<vector< int>>& result,vector< int>& keys,vector< int>& count,vector< int>& v, int dep)
    {
         // add in the result
         if(dep==keys.size())
        {
            vector< int> newv;
             for( int i= 0;i<dep;i++)
                 for( int j= 0;j<v[i];j++)
                    newv.push_back(keys[i]);
            result.push_back(newv);
             return;
        }
         // generate with next key
         for( int i= 0;i<=count[dep];i++)
        {
            v[dep]=i;
            generate(result,keys,count,v,dep+ 1);
        }
    }
};