public class ThreadedBinaryTreeDemo {
public static void main(String[] args) {
// 先创建一棵二叉树
ThreadedBinaryTree binaryTree = new ThreadedBinaryTree();
// 创建需要的结点
HeroNode root = new HeroNode(1, "宋江");
HeroNode node2 = new HeroNode(3, "吴用");
HeroNode node3 = new HeroNode(6, "卢俊义");
HeroNode node4 = new HeroNode(8, "林冲");
HeroNode node5 = new HeroNode(10, "关胜");
HeroNode node6 = new HeroNode(14, "武松");
binaryTree.setRoot(root);
root.setLeft(node2);
root.setRight(node3);
// 设置父结点
node2.setParent(root);
node3.setParent(root);
node2.setLeft(node4);
node2.setRight(node5);
// 设置父结点
node4.setParent(node2);
node5.setParent(node2);
node3.setLeft(node6);
// 设置父结点
node6.setParent(node3);
// 测试中序
// 测试线索化
// binaryTree.threadedNodes(root); //8,3,10,1,14,6
//
// HeroNode leftNode = node5.getLeft();
// HeroNode rightNode = node5.getRight();
// System.out.println(leftNode.getNo()+" "+leftNode.getName());
// System.out.println(rightNode.getNo()+" "+rightNode.getName());
//
// // 遍历线索化二叉树
// binaryTree.threadedList();
// 测试后序
// 测试线索化
binaryTree.threadedNodesPost(root); //8,10,3,14,6,1
HeroNode leftNode = node6.getLeft();
HeroNode rightNode = node6.getRight();
System.out.println(leftNode.getNo()+" "+leftNode.getName());
System.out.println(rightNode.getNo()+" "+rightNode.getName());
// 遍历线索化二叉树
binaryTree.threadedListPost();
}
}
class ThreadedBinaryTree{
private HeroNode root;
private HeroNode pre; // 线索化使用,总是指向当前结点的前驱结点
public void setRoot(HeroNode root) {
this.root = root;
}
// 对二叉树进行中序线索化
public void threadedNodes(HeroNode node){
if(null == node) {
return;
}
// 中序线索化,先线索化左子树,再线索化当前结点,最后线索话右子树
// 1.先线索化左子树
threadedNodes(node.getLeft());
// 2.再线索化当前结点
if(node.getLeft() == null){
node.setLeft(pre);
node.setLeftType(1);
}
// 处理后继结点
if(null != pre && pre.getRight() == null){
// 让前驱结点的右指针指向当前结点
pre.setRight(node);
// 改变类型
pre.setRightType(1);
}
// 让当前结点成为下一个结点的前驱结点
pre = node;
// 3.再线索化右子树
threadedNodes(node.getRight());
}
// 中序遍历线索化二叉树的方法
public void threadedList(){
// 定义一个变量,存储当前遍历的结点,从root开始
HeroNode node = root;
while(null != node){
while(node.getLeftType() == 0){
node = node.getLeft();
}
System.out.println(node);
while(node.getRightType() == 1){
node = node.getRight();
System.out.println(node);
}
node = node.getRight();
}
}
// 对二叉树进行后序线索化
public void threadedNodesPost(HeroNode node){
if(null == node) {
return;
}
// 后序线索化,先线索化左子树,再线索话右子树,最后线索化当前结点
// 1.先线索化左子树
threadedNodesPost(node.getLeft());
// 2.再线索化右子树
threadedNodesPost(node.getRight());
// 3.最后线索化当前结点
if(node.getLeft() == null){
node.setLeft(pre);
node.setLeftType(1);
}
// 处理后继结点
if(null != pre && pre.getRight() == null){
// 让前驱结点的右指针指向当前结点
pre.setRight(node);
// 改变类型
pre.setRightType(1);
}
// 让当前结点成为下一个结点的前驱结点
pre = node;
}
//后序遍历线索化二叉树可以参考该博客
// 后序遍历线索化二叉树的方法, 后序遍历线索话二叉树需要利用父结点
public void threadedListPost(){
// 定义一个变量,存储当前遍历的结点,从root开始
HeroNode node = root;
while(null != node && node.getLeftType() == 0){
node = node.getLeft();
}
while(null != node){
//右节点是线索
if(node.getRightType() == 1){
System.out.println(node);
pre = node;
node = node.getParent();
}else{
//如果上个处理的节点是当前节点的右节点
if(node.getRight() == pre){
System.out.println(node);
if(node == root){
return;
}
pre = node;
node = node.getParent();
}else{
node = node.getRight();
while(null != node && node.getLeftType() == 0){
node = node.getLeft();
}
}
}
}
}
}
class HeroNode{
private int no;
private String name;
private HeroNode left; // 默认为null
private HeroNode right; // 默认为null
//leftType == 0, 表示指向左子树. leftType == 1, 表示指向前驱结点.
//rightType == 0, 表示指向右子树. rightType == 1, 表示指向后继结点.
private int leftType;
private int rightType;
public HeroNode getParent() {
return parent;
}
public void setParent(HeroNode parent) {
this.parent = parent;
}
private HeroNode parent; // 父结点的指针
public HeroNode(int no, String name) {
this.no = no;
this.name = name;
}
public int getLeftType() {
return leftType;
}
public void setLeftType(int leftType) {
this.leftType = leftType;
}
public int getRightType() {
return rightType;
}
public void setRightType(int rightType) {
this.rightType = rightType;
}
public int getNo() {
return no;
}
public void setNo(int no) {
this.no = no;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public HeroNode getLeft() {
return left;
}
public void setLeft(HeroNode left) {
this.left = left;
}
public HeroNode getRight() {
return right;
}
public void setRight(HeroNode right) {
this.right = right;
}
@Override
public String toString() {
return "HeroNode{" +
"no=" + no +
", name='" + name + '\'' +
'}';
}
}