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],  []]

没有什么区别，就是往前挪两下指针。。。。

class Solution {public:    vector<vector<int> > subsetsWithDup(vector<int> &S) {        vector<vector<int> > res;        vector<int> solution;        res.push_back(solution);        if (S.size()==0)            return res;        sort(S.begin(), S.end());        helper(res,solution,S,0);        return res;    }   void helper(vector< vector<int> >& res, vector<int>& solution, vector<int>& input, int level){    for (int i=level; i<input.size();i++){    solution.push_back(input[i]);    res.push_back(solution);    helper(res,solution,input,i+1);    solution.pop_back();    while(i<input.size()-1 && input[i]==input[i+1])        i++;    }    }};