二叉树的前中后序代码秒懂

public class BinaryTreeDome {
    public static void main(String[] args) {
        BinaryTree binaryTree = new BinaryTree();
        //创建节点
        HeroNode R1 = new HeroNode(1,"宋江");
        HeroNode R2 = new HeroNode(2,"吴用");
        HeroNode R3 = new HeroNode(3,"卢俊义");
        HeroNode R4 = new HeroNode(4,"林冲");
        HeroNode R5 = new HeroNode(5,"关胜");
        //手动创建二叉树
        R1.setLeft(R2);
        R1.setRight(R3);
        R3.setLeft(R5);
        R3.setRight(R4);
        binaryTree.setRoot(R1);
        //测试
        System.out.println("前序遍历");
        binaryTree.preOrder();
        System.out.println("中序遍历");
        binaryTree.infixOrder();
        System.out.println("后续遍历");
        binaryTree.postOrder();
    }
}
//定义一个二叉树
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，无法遍历");
        }
    }
    //中序遍历
    public void postOrder() {
        if (this.root != null) {
            this.root.postOrder();
        } else {
            System.out.println("二叉树为空，无法遍历");
        }
    }
}

    //实体类
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;
    }

    @Override
    public String toString() {
        return "HeroNode{" +
                "no=" + no +
                ", 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;
    }
    //编写前序遍历
    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();
        }
    }
    //中序遍历
    public void infixOrder(){
        //递归向左子树前序遍历
        if (this.left!=null){
            this.left.infixOrder();
        }
        System.out.println(this);//先输出父节点
        //递归向右子树前序遍历
        if (this.right!=null){
            this.right.infixOrder();
        }
    }
    //后序遍历
    public void postOrder(){
        //递归向左子树前序遍历
        if (this.left!=null){
            this.left.postOrder();
        }
        //递归向右子树前序遍历
        if (this.right!=null){
            this.right.postOrder();
        }
        System.out.println(this);//先输出父节点
    }
    }

前序遍历
HeroNode{no=1, name='宋江'}
HeroNode{no=2, name='吴用'}
HeroNode{no=3, name='卢俊义'}
HeroNode{no=5, name='关胜'}
HeroNode{no=4, name='林冲'}
中序遍历
HeroNode{no=2, name='吴用'}
HeroNode{no=1, name='宋江'}
HeroNode{no=5, name='关胜'}
HeroNode{no=3, name='卢俊义'}
HeroNode{no=4, name='林冲'}
后续遍历
HeroNode{no=2, name='吴用'}
HeroNode{no=5, name='关胜'}
HeroNode{no=4, name='林冲'}
HeroNode{no=3, name='卢俊义'}
HeroNode{no=1, name='宋江'}

 看父节点

第一输出：前序

第二输出：中序

最后输出：后序