leetcode 90 子集II

先一路走到黑，然后再一步一步往回走。回溯没毛病。

class Solution {
public:
    vector<vector<int>> res;
   
    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
         if(nums.empty()){
            return res;
        }
     set<vector<int>> temp;
    vector<int> ans;
     dfs(0,nums,temp,ans);
        for(auto ff:temp)
        {
            res.push_back(ff);
        }
    return res;
    }
    void dfs(int pos,vector<int> num, set<vector<int>>& filter ,vector<int> ans)
    {
        if(pos==num.size())
        {
            sort(ans.begin(), ans.end());
            filter.insert(ans);
            return;
        }
        dfs(pos+1,num,filter,ans);
        ans.push_back(num[pos]);
       dfs(pos+1,num,filter,ans);
    }
};