Subsets

Given a set of distinct integers, 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 = [1,2,3], a solution is:

[ [3], [1], [2], [1,2,3], [1,3], [2,3], [1,2], [] ]

class  Solution {
public:
    vector<vector< int> > subsets(vector< int> &S) {
        vector<vector< int> > result;
        
         // sort s
         for( int i= 0;i<S.size();i++)
          for( int j=i+ 1;j<S.size();j++)
         {
              if(S[i]>S[j])
             {
                  int tmp=S[i];
                 S[i]=S[j];
                 S[j]=tmp;
             }
         }
         
        vector< int> v;
         for( int i= 0;i<S.size();i++) v.push_back( 0);
        
        gen(result,v,S, 0, 0,S.size());
         return result;
    }
     void gen(vector<vector< int> >& result,vector< int>& v,vector< int> &S, int dep, int index, int size)
    {
        vector< int> vnew;
         for( int i= 0;i<dep;i++)
            vnew.push_back(v[i]);
        result.push_back(vnew);
        
         for( int i=index;i<size;i++)
        {
            v[dep]=S[i];
            gen(result,v,S,dep+ 1,i+ 1,size);
        }
    }
};