二叉树-查找指定节点

并分别使用三种查找方式，查找 heroNO = 5 的节点

代码示例：

package com.wxit.tree;

/**
 * @Author wj
 **/
public class BinaryTreeDemo {
    public static void main(String[] args) {
        //先创建一颗二叉树
        BinaryTree binaryTree = new BinaryTree();
        //创建需要的节点
        HeroNode root = new HeroNode(1, "吴杰");
        HeroNode node2 = new HeroNode(2, "吴昊");
        HeroNode node3 = new HeroNode(3, "小昊");
        HeroNode node4 = new HeroNode(4, "张三");
        HeroNode node5 = new HeroNode(5, "李婷");

        //先手动创建二叉树
        root.setLeft(node2);
        root.setRight(node3);
        node3.setRight(node4);
        node3.setLeft(node5);
        binaryTree.setRoot(root);

        //测试
        System.out.println("前序遍历");
        binaryTree.preOrder();

        System.out.println("中序遍历");
        binaryTree.infixOrder();

        System.out.println("后序遍历");
        binaryTree.postOrder();

        //测试
        System.out.println("前序遍历查找");
        HeroNode resNode = binaryTree.preOrderSearch(5);
        if (resNode != null){
            System.out.printf("找到了,信息为no=%d name=%s",resNode.getNo(),resNode.getName());
        } else {
            System.out.printf("没有找到no = %d 的英雄",5);
        }
    }
}

//创建HeroNode节点
class HeroNode{
    private int no;
    private String name;
    private HeroNode left;
    private HeroNode right;

    public HeroNode(int no, String name) {
        this.no = no;
        this.name = name;
    }

    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 + '\'' +
                '}';
    }

    //编写前序遍历的方法
    public void preOrder(){
        System.out.println(this);//先输出父节点
        //递归向左子树前序遍历
        if (this.left != null){
            this.left.preOrder();
        }
        //递归向右子树前序遍历
        if (this.right != null){
            this.right.preOrder();
        }
    }

    //编写中序遍历的方法
    public void infixOrder(){
        //递归向左子树中序遍历
        if (this.left != null){
            this.left.infixOrder();
        }
        //输出父节点
        System.out.println(this);
        //递归向右子树中序遍历
        if (this.right != null){
            this.right.infixOrder();
        }
    }

    //编写后序遍历的方法
    public void postOrder(){
        if (this.left != null){
            this.left.postOrder();
        }
        if (this.right != null){
            this.right.postOrder();
        }
        System.out.println(this);
    }

    //前序遍历查找
    public HeroNode preOrderSearch(int no){
        //比较当前节点是不是
        if (this.no == no){
            return this;
        }
        //判断当前节点的左子节点是否为空,如果不为空,则递归前序查找,如果左递归前序查找，找到节点，则返回
        HeroNode resNode = null;
        if (this.left != null){
            resNode = this.left.preOrderSearch(no);
        }
        if (resNode != null){
            //说明左子树找到
            return resNode;
        }
        //左子节点没有找到，继续判断，判断当前节点的右子节点是否为空,如果不为空，就继续向右递归查找
        if (this.right != null){
            resNode = this.right.preOrderSearch(no);
        }
        return resNode;
    }

    //中序遍历查找
    public HeroNode infixOrderSearch(int no){
        //判断当前节点的左子节点是否为空,如果不为空,则递归中序查找
        HeroNode resNode = null;
        if (this.left != null){
            resNode = this.left.infixOrderSearch(no);
        }
        if (resNode != null){
            return resNode;
        }
        //没找到，就和当前节点比较,如果是，就返回
        if (this.no == no){
            return this;
        }
        //否则继续向右递归进行中序查找
        if (this.right != null){
            resNode = this.right.infixOrderSearch(no);
        }
        return resNode;
    }

    //后序遍历查找
    public HeroNode postOrderSearch(int no){
        //判断当前节点的左子节点是否为空,如果不为空,则递归后序查找
        HeroNode resNode = null;
        if (this.left != null){
            resNode = this.left.postOrderSearch(no);
        }
        if (resNode != null){
            return resNode;
        }
        //如果左子树没有找到,则向右子树递归进行后序遍历查找
        if (this.right != null){
            resNode = this.right.postOrderSearch(no);
        }
        if (resNode != null){
            return resNode;
        }
        //如果右子树没有找到,就比较当前节点是不是
        if (this.no == no){
            return this;
        }
        return resNode;
    }
}

//定义二叉树
class BinaryTree{
    private HeroNode root;

    public void setRoot(HeroNode root){
        this.root = root;
    }

    //前序遍历
    public void preOrder(){
        if (this.root != null){
            this.root.preOrder();
        } else {
            System.out.println("二叉树为空,无法遍历");
        }
    }

    //中序遍历
    public void infixOrder(){
        if (this.root != null){
            this.root.infixOrder();
        } else {
            System.out.println("二叉树为空,不能遍历");
        }
    }

    //后去遍历
    public void postOrder(){
        if (this.root != null){
            this.root.postOrder();
        } else {
            System.out.println("二叉树为空,不能遍历");
        }
    }

    //前序遍历
    public HeroNode preOrderSearch(int no){
        if (root != null){
            return root.preOrderSearch(no);
        }else {
            return null;
        }
    }

    //中序遍历
    public HeroNode infixOrderSearch(int no){
        if (root != null){
            return root.infixOrderSearch(no);
        } else {
            return null;
        }
    }

    //后序遍历
    public HeroNode postOrderSearch(int no){
        if (root != null){
            return postOrderSearch(no);
        } else {
            return null;
        }
    }
}