subset

递归

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> result;
        vector<int> res;
        sort(nums.begin(),nums.end());
        sub_core(result,res,nums,0);
        return result;
    }
    void sub_core(vector<vector<int>> &result,vector<int> &res,vector<int> nums,int start){
        result.push_back(res);
        for(int i = start;i < nums.size();i++){
            res.push_back(nums[i]);
            sub_core(result,res,nums,i+1);
            res.pop_back();
        }
    }
};