leetcode78——子集——回溯

 回溯题解：

class Solution {
    List> root=new ArrayList<>();
    List list=new ArrayList<>();
    public List> subsets(int[] nums) {
        DFS(nums,0);
        return root;
    }

    public void DFS(int[] nums,int start){
        if(start==nums.length){
            root.add(new ArrayList(list));
            return;
        }

        list.add(nums[start]);
        DFS(nums,start+1);
        list.remove(list.size()-1);
        DFS(nums,start+1);
    }
}