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Traverse.java
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175 lines (147 loc) · 4.14 KB
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package com.kagura.tree;
import static java.lang.System.*;
import org.junit.Test;
/**
* @author <a href="mailto:hongwen0928@outlook.com">Karas</a>
* @date 2019/11/30
* @since 1.0.0
*/
public class Traverse {
class Node {
private int data;
private Node left;
private Node right;
public Node() {
}
public Node(int data, Node left, Node right) {
this.data = data;
this.left = left;
this.right = right;
}
public int getData() {
return data;
}
public void setData(int data) {
this.data = data;
}
public Node getLeft() {
return left;
}
public void setLeft(Node left) {
this.left = left;
}
public Node getRight() {
return right;
}
public void setRight(Node right) {
this.right = right;
}
@Override
public String toString() {
return String.valueOf(data);
}
}
public void printNode(Node node) {
if (node != null) {
System.out.print(node.getData() + " ");
}
}
/**
* 先序递归
* （找到根，先记录根）
*
* @param node 根节点
*/
public void perOrder(Node node) {
if (node == null) {
return;
}
printNode(node);
perOrder(node.left);
perOrder(node.right);
}
/**
* 中序递归
* （先记录根的所有左子）
*
* @param node 根节点
*/
public void inOrder(Node node) {
if (node == null) {
return;
}
inOrder(node.left);
printNode(node);
inOrder(node.right);
}
/**
* 后序递归
* （先记录根的所有子节点）
*
* @param node 根节点
*/
public void postOrder(Node node) {
if (node == null) {
return;
}
postOrder(node.left);
postOrder(node.right);
printNode(node);
}
public Node getTree() {
Node node7 = new Node(7, null, null);
Node node9 = new Node(9, null, null);
Node node8 = new Node(8, node7, node9);
Node node3 = new Node(3, null, null);
Node node5 = new Node(5, null, null);
Node node4 = new Node(4, node3, node5);
Node node1 = new Node(1, null, null);
Node node2 = new Node(2, node1, node4);
return new Node(6, node2, node8);
}
@Test
public void traverse01() {
// 前序 6 2 1 4 3 5 8 7 9 根左右
System.out.println("先序遍历");
perOrder(getTree());
// 中序 1 2 3 4 5 6 7 8 9 左根右
System.out.println("\n中序遍历");
inOrder(getTree());
// 后序 1 3 5 4 2 7 9 8 6 左右根
System.out.println("\n后序遍历");
postOrder(getTree());
}
@Test
public void morris() {
// Morris Traverse
morrisInorderTraverse(getTree());
}
private void morrisInorderTraverse(Node root) {
Node cur = root;
while (cur != null) {
if (cur.left == null) {
// 如果没有左子，直接走右子
out.println(cur);
cur = cur.right;
} else {
Node pre = cur.left;
// 用来遍历到最右
while(pre.right != null && pre.right != cur) {
pre = pre.right;
}
if (pre.right == cur) {
// 意味着前驱节点的右节点已被设置，该次遍历为回溯
// 左边已经搞定，接下来需要处理右边
pre.right = null;
out.println(cur + " 线索回归打印");
cur = cur.right;
} else {
// 第一次访问该前驱节点，设置线索，即右节点为当前节点
pre.right = cur;
out.println(String.format("%s 设置线索(%s)", cur, pre));
cur = cur.left;
}
}
}
}
}