590. N叉树的后序遍历

590. N-ary Tree Postorder Traversal

题目描述

给定一个 N 叉树，返回其节点值的后序遍历。

LeetCode590. N-ary Tree Postorder Traversal

例如，给定一个 3 叉树:

返回其后序遍历: [5,6,3,2,4,1].

说明: 递归法很简单，你可以使用迭代法完成此题吗?

Java 实现

Iterative Solution

import java.util.LinkedList;import java.util.List;import java.util.Stack;class Node {    public int val;    public List
    
      children;    public Node() {    }    public Node(int _val, List
     
       _children) {        val = _val;        children = _children;    }}class Solution {    public List
      
        postorder(Node root) {        List
       
         result = new LinkedList<>();        if (root == null) {            return result;        }        Stack
        
          stack = new Stack<>();        stack.push(root);        while (!stack.isEmpty()) {            Node node = stack.pop();            for (Node child:node.children){                stack.push(child);            }            result.add(0, node.val);        }        return result;    }}
        
       
      
     
    

Recursive Solution

import java.util.LinkedList;import java.util.List;class Node {    public int val;    public List
    
      children;    public Node() {    }    public Node(int _val, List
     
       _children) {        val = _val;        children = _children;    }}class Solution {    List
      
        result = new LinkedList<>();    public List
       
         postorder(Node root) {        if (root == null) {            return result;        }        List
        
          node = root.children;        for (int i = 0; i < node.size(); i++) {            postorder(node.get(i));        }        result.add(root.val);        return result;    }}
        
       
      
     
    

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