Leetcode590 N叉树的后序遍历

　　很简单的题目，但是多叉树的操作也是蛮重要的。比如实现 B 树 B+ 树时，这些操作都要用到，所以写一下。

　　JAVA：

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 {
        List<Integer> list = new LinkedList<Integer>();

        public List<Integer> postorder(Node root) {
            if (root == null) return list;
            List<Node> children = root.children;
            for (Node node : children) {
                postorder(node);
            }
            list.add(root.val);
            return list;
        }

　　JS：

/**
 * // Definition for a Node.
 * function Node(val,children) {
 *    this.val = val;
 *    this.children = children;
 * };
 */

/**
 * @param {Node} root
 * @return {number[]}
 */
var postorder = (root) => {
    let reList = [];
    return helper(root, reList);
}

var helper = (root, reList) => {
    if (!root) return re;
    let children = root.children;
    for (let i = 0; i < children.length; i++) helper(children[i], reList);
    reList.push(root.val);
    return reList;
};