33.Subsets-子集

题目描述：


解析：回溯法

class Solution {
    //存放结果
    List<List<Integer>> res = new ArrayList<>();
    //存放当前路径
    List<Integer> path = new ArrayList<>();
    public List<List<Integer>> subsets(int[] nums) {
        dfs(nums, 0);
        return res;
    }
    private void dfs(int[] nums, int start) {
        //一上来就直接添加节点
        res.add(new ArrayList<>(path));
        for (int i = start; i < nums.length; i++) {
            path.add(nums[i]);
            System.out.println(" 递归之前 => " + path);
            //从下一个节点开始递归下一层
            dfs(nums, i + 1);
            //回溯
            path.remove(path.size() - 1);
            System.out.println("递归之后 => " + path);
        }
    }
}