二叉树的后序遍历(递归vs非递归)Java

import java.util.ArrayList; import java.util.List; import java.util.Stack;  public class PostOrder {     //后序遍历，非递归     public static void postOrderNoR(Node root) {         Stack<Node> stack = new Stack<>();         Node cur = root;         Node last = null; //上一次被三次完整经过的结点         while (!stack.empty() || cur != null) {             while (cur != null) {                 stack.push(cur);                 cur = cur.left;             }              Node top = stack.peek();//取栈顶元素，不删除             if (top.right == null || top.right == last) {                 stack.pop();//取栈顶元素，删除                 System.out.println(top.value);                 last = top;             } else {                 cur = top.right;             }         }     }      //后序递归遍历1     public static List<Integer> list;     private static void postOrder(Node root) {         if (root == null) {             return;         }         postOrder(root.left);         postOrder(root.right);         list.add(root.value);     }     public static List<Integer> postOrderTraversal(Node root) {         list = new ArrayList<>();         postOrder(root);         return list;     }      //后序递归遍历2     public static void postOrderTraversal2(Node root) {         if (root == null) {             return;         }         postOrderTraversal2(root.left);         postOrderTraversal2(root.right);         System.out.println(root.value);     }      public static void main(String[] args) {         Node n1 = new Node(1);         n1.left = new Node(2);         n1.right = new Node(3);         n1.left.left = new Node(4);         n1.left.right = new Node(5);         n1.right.right = new Node(6);          postOrderNoR(n1);         System.out.println("====");         List<Integer> list = postOrderTraversal(n1);         System.out.println(list);         System.out.println("====");         postOrderTraversal2(n1);     } } 

来源：51CTO

作者：ML冲啊哈

链接：https://blog.csdn.net/qq_44781020/article/details/100083063