leetcode-78：子集

输入：nums = [1,2,3]
输出：[[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]

输入：nums = [0]
输出：[[],[0]]

class Solution {
public:
    vector<vector<int>> res;
    vector<int> path;
    void backtracing(vector<int>& nums,int startIndex){
        res.push_back(path);
        for(int i=startIndex;i<nums.size();i++){
            path.push_back(nums[i]);
            backtracing(nums,i+1);
            path.pop_back();
        }
    }
    vector<vector<int>> subsets(vector<int>& nums) {
        backtracing(nums,0);
        return res;
    }
};

class Solution {
    List<List<Integer>> res=new LinkedList<>();
    List<Integer> path=new LinkedList<>();
    void dfs(int[] nums,int startIndex){
        res.add(new LinkedList<>(path));
        for(int i=startIndex;i<nums.length;i++){
            path.add(nums[i]);
            dfs(nums,i+1);
            path.remove(path.size()-1);
        }
    }
    public List<List<Integer>> subsets(int[] nums) {
        dfs(nums,0);
        return res;
    }
}