Java LeetCode 589. N叉树的前序遍历

给定一个 N 叉树，返回其节点值的前序遍历。

/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> children;

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

    public Node(int _val, List<Node> _children) {
        val = _val;
        children = _children;
    }
};
*/

class Solution {
    
    
    public List<Integer> preorder(Node root) {
    
    
        List<Integer> list = new ArrayList();
        reverse(root,list);
        return list;
    }
    public void reverse(Node root,List list){
    
    
        if(root==null){
    
    
            return;
        }
        list.add(root.val);
        List<Node> childrens = root.children;
        if(childrens!=null&&childrens.size()>0){
    
    
             for(Node no:childrens){
    
    
                    reverse(no,list);
                }
        }
    }
}