二叉树的概念

二叉树遍历的说明

使用前序，中序和后序对下面的二叉树进行遍历.

二叉树遍历应用实例(前序,中序,后序)

应用实例的说明和思路

代码实现

package com.iflytek.tree;

//先创建HeroNode 结点
class HeroNode{
    private int no;
    private String name;
    private HeroNode left;//默认 null
    private HeroNode right;//默认 null

    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);//先输出父结点
        //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();
        }
    }
    //中序遍历
    public void infixOrder(){
        //递归向左子树中序遍历
        if (this.left!=null){
            this.left.infixOrder();
        }
        //输出父结点
        System.out.println(this);
        //递归向右子树中序遍历
         if (this.right!=null){
             this.right.infixOrder();
         }
    }
    //后序遍历
    public void postOrder(){
        //递归向左子树中序遍历
        if (this.left!=null){
            this.left.postOrder();
        }
        //递归向右子树中序遍历
        if (this.right!=null){
            this.right.postOrder();
        }
        //输出父结点
        System.out.println(this);
    }
}
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，无法遍历");
        }
    }
    //后序遍历
    public void postOrder(){
        if (this.root!=null){
            this.root.postOrder();
        }else {
            System.out.println("二叉树为空，无法遍历");
        }
    }

}
public class BinaryTreeDemo {
    public static void main(String[] args) {
        //先需要创建一颗二叉树
        BinaryTree binaryTree=new BinaryTree();
        //创建需要的结点
        HeroNode root=new HeroNode(1,"宋江");
        HeroNode node2=new HeroNode(2,"吴用");
        HeroNode node3=new HeroNode(3,"卢俊义");
        HeroNode node4=new HeroNode(4,"林冲");
        HeroNode node5=new HeroNode(5,"关胜");
        //说明，我们先手动创建该二叉树，后面我们学习递归的方式创建二叉树
        root.setLeft(node2);
        root.setRight(node3);
        node3.setRight(node4);
        node3.setLeft(node5);
        binaryTree.setRoot(root);

        //测试
        System.out.println("前序遍历"); // 1,2,3,5,4
        binaryTree.preOrder();
        //测试
        System.out.println("中序遍历");
        binaryTree.infixOrder(); // 2,1,5,3,4
        //测试
        System.out.println("后序遍历");
        binaryTree.postOrder(); // 2,5,4,3,1
    }
}