二叉树的三叉链表存储（java实现）

package com.fcy.dataStruct;
/**
* 与二叉树的二叉链表存储相比，三叉链表存储
* 多了一个指针域来记录当前节点的父节点
*/
class ThreeLinkBinTree<E>{
public static class TreeNode{
Object data;
TreeNode left;           //左子节点
TreeNode right;			 //右子节点
TreeNode parent;         //父节点
public TreeNode(){

}
public TreeNode(Object data){
this.data=data;
}
public TreeNode(Object data,TreeNode left,TreeNode right,TreeNode parent){
this.data=data;
this.left=left;
this.right=right;
this.parent=parent;
}
}
private TreeNode root;
public ThreeLinkBinTree(){
this.root=new TreeNode();
}
//以指定根元素来创建二叉树
public ThreeLinkBinTree(E data){
this.root=new TreeNode(data);
}
/**
* 为指定节点添加子节点
* @param parent 新子节点的父节点
* @param data 新子节点的数据
* @param isLeft 是否为左子节点
* @return 新增的节点
*/
public TreeNode addNode(TreeNode parent,E data,boolean isLeft){
if(parent==null){
throw new RuntimeException(parent+"节点为null,无法添加子节点");
}
if(isLeft&&parent.left!=null){
throw new RuntimeException(parent+"节点已有左子节点，无法添加左子节点");
}
if(!isLeft&&parent.right!=null){
throw new RuntimeException(parent+"节点已有右子节点，无法添加右子节点");
}
TreeNode newNode=new TreeNode(data);
if(isLeft){
//让父节点的left引用指向新节点
parent.left=newNode;
}else{
//让父节点的right引用指向新节点
parent.right=newNode;
}
//让新节点的parent引用到parent节点
newNode.parent=parent;
return newNode;
}
//判断二叉树是否为空
public boolean empty(){
return root.data==null;
}
//返回根节点
public TreeNode root(){
if(empty()){
throw new RuntimeException("树为空，无法访问根节点");
}
return root;
}
//返回指定节点（非根节点）的父节点
public E parent(TreeNode node){
if(node==null){
throw new RuntimeException(node+"节点为Null，无法访问其父节点！");
}
return (E)node.parent.data;
}
//返回指定节点（非叶子）的左子节点
public E leftChild(TreeNode parent){
if(parent==null){
throw new RuntimeException("节点为Null,无法添加子节点");
}
return parent.left==null?null:(E)parent.left.data;
}
//返回指定节点（非叶子）的右子节点
public E rightChild(TreeNode parent){
if(parent==null){
throw new RuntimeException(parent+"节点为null，无法添加子节点");
}
return parent.right==null?null:(E)parent.right.data;
}
//返回二叉树的深度
public int deep(){
return deep(root);
}
//递归，每棵子树的深度为其所有子树的最大深度+1
private int deep(TreeNode node){
if(node==null){
return 0;
}
//没有子树
if(node.left==null&&node.right==null){
return 1;
}else{
int leftDeep=deep(node.left);
int rightDeep=deep(node.right);
//记录其所有左、右子树中较大的深度
int max=leftDeep>rightDeep?leftDeep:rightDeep;
//返回其左、右子树中较大的深度+1
return max+1;
}
}
}
public class ThreeLinkBinDemo {
public static void main(String[] args) {
ThreeLinkBinTree<String> binTree=new ThreeLinkBinTree<>("根节点");
ThreeLinkBinTree.TreeNode tn1=binTree.addNode(binTree.root(),"第二层左节点",true);
ThreeLinkBinTree.TreeNode tn2=binTree.addNode(binTree.root(),"第二层右节点",false);
ThreeLinkBinTree.TreeNode tn3=binTree.addNode(tn2,"第三层左节点",true);
ThreeLinkBinTree.TreeNode tn4=binTree.addNode(tn2,"第三层右节点",false);
ThreeLinkBinTree.TreeNode tn5=binTree.addNode(tn3,"第四层左节点",true);
System.out.println("tn2的左子节点："+binTree.leftChild(tn2));
System.out.println("tn2的右子节点："+binTree.rightChild(tn2));
System.out.println("tn3的父节点："+binTree.parent(tn3));
System.out.println(binTree.deep());
}
}