90. Subsets II

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

Note: The solution set must not contain duplicate subsets.

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

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

class Solution {public:    vector<vector<int>> subsetsWithDup(vector<int>& nums)     {        vector<vector<int> >ret;        if(nums.empty())            return ret;        sort(nums.begin(),nums.end());        vector<int>temp;        ret.push_back(temp);        dfs(nums,0,temp,ret);        return ret;    }    void dfs(vector<int>& nums,int pos,vector<int>&temp,vector<vector<int> >&ret)    {        if(pos==nums.size())            return;        for(int i=pos;i<nums.size();i++)        {            if(i!=pos&&nums[i]==nums[i-1])                continue;            temp.push_back(nums[i]);            ret.push_back(temp);            dfs(nums,i+1,temp,ret);            temp.pop_back();        }    }};