78. 子集

 1 //直接套模板
 2 class Solution 
 3 {
 4     vector<vector<int>> res;
 5     void helper(vector<int>& nums, int start, vector<int>& out)
 6     {
 7         res.push_back(out);
 8 
 9         for (int i = start; i < nums.size(); ++i)
10         {
11             out.push_back(nums[i]);
12             helper(nums, i + 1, out);
13             out.pop_back();
14         }
15     }
16 public:
17     vector<vector<int>> subsets(vector<int>& nums) 
18     {
19         vector<int> out;
20         helper(nums,0,out);
21         return res;
22     }
23 };