题目链接/文章讲解：https://programmercarl.com/0078.%E5%AD%90%E9%9B%86.html

视频讲解：https://www.bilibili.com/video/BV1U84y1q7Ci

1.本题取子集，与之前取集合的区别就是这个每走一步都收获一次结果。

CPP

class Solution {
public:
    vector<int> path;
    vector<vector<int>> res;
    
    void backtracking(vector<int>& nums, int startIndex){
        res.push_back(path);
        if(startIndex >= nums.size())return ;

        for(int i = startIndex; i < nums.size(); i++){
            path.push_back(nums[i]);
            backtracking(nums, i + 1);
            path.pop_back();
        }
        return ;
    }
    vector<vector<int>> subsets(vector<int>& nums) {
        path.clear();
        res.clear();
        backtracking(nums, 0);
        return res;
    }
};