数组的子集Subsets 不能重复

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: [1,2,2]
Output:
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]

class Solution {

public:
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
        vector<int> ivec;
        set<vector<int> > z;
        vector<vector<int> > res;
        sort(nums.begin(),nums.end());  // 排序是为了去重复
        genesub(nums,0,ivec,z);
        
        set<vector<int> >::iterator iter;
        for(iter=z.begin();iter!=z.end();++iter){
            res.push_back(*iter);
        }
        return res;
    }
    
    void genesub(vector<int> &nums,int k,vector<int> temp,set<vector<int> > &res){
        res.insert(temp);
        
        for(int i=k;i<nums.size();++i){
            temp.push_back(nums[i]);
            genesub(nums,i+1,temp,res);
            temp.pop_back();
        }
    }
};