78.子集

78.子集

思路：回溯

class Solution {
public:
    vector<int>tmp;
    vector<vector<int>>res;
    vector<vector<int>> subsets(vector<int>& nums) {
        backtrack(0,nums);
        res.push_back({});
        return res;
    }
    void backtrack(int start,vector<int>& nums){
        if(start>=nums.size()){
            return;
        }
        for(int i=start;i<nums.size();i++){
            tmp.push_back(nums[i]); //添加每一个“结点”
            res.push_back(tmp);
            backtrack(i+1,nums);
            tmp.pop_back();
        }
    }
};