数据结构 - 二叉树(删除节点)

因为二叉树是单向的，所以要判断当前节点的子节点(左或右)是否是被删除的节点

    //递归删除节点
    //规定：如果是叶子节点就删除节点，如果非叶子节点就删除子树
    public void delNode(int no){
        if (this.left !=null && this.left.no == no){
            this.left = null;
            return;
        }
        if (this.right != null && this.right.no == no){
            this.right = null;
            return;
        }
        if (this.left != null){
            this.left.delNode(no);
        }
        if (this.right != null){
            this.right.delNode(no);
        }

    }

    //删除节点
    public void delNode(int no){
        if (root != null){//判断root是不是要删除的节点
            if (root.getNo() == no){
                root = null;
            }else {
                root.delNode(no);
            }
        }
    }

完整代码

package tree;

public class BinaryTreeDemo {
    public static void main(String[] args) {
        //先需要创建一颗二叉树
        BinaryTree binaryTree = new BinaryTree();

        //创建需要的节点
        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，先手动创建该二叉树，后面学习递归方式创建二叉树
        binaryTree.setRoot(root);
        root.setLeft(node2);
        root.setRight(node3);
        node3.setRight(node4);
        node3.setLeft(node5);

        //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();

        //测试查找
        //前序遍历查找
//        System.out.println("前序遍历查找：~~~~");
//        HeroNode heroNode1 = binaryTree.preOrederSearch(5);
//        if (heroNode1 != null){
//            System.out.println("找到节点：" + heroNode1.toString());
//        }else {
//            System.out.println("没有找到");
//        }
//
////        //中序遍历查找
//        System.out.println("中序遍历查找：~~~~");
//        HeroNode heroNode2 = binaryTree.infixOrderSeach(5);
//        if (heroNode2 != null){
//            System.out.println("找到节点：" + heroNode2.toString());
//        }else {
//            System.out.println("没有找到");
//        }
//
//        //后序遍历查找
//        System.out.println("后序遍历查找：~~~~");
//        HeroNode heroNode3 = binaryTree.postOrderSeach(5);
//        if (heroNode3 != null){
//            System.out.println("找到节点：" + heroNode3.toString());
//        }else {
//            System.out.println("没有找到");
//        }


        //删除前
        System.out.println("删除前，前序遍历");
        binaryTree.preOrder();
        binaryTree.delNode(3);
        System.out.println("删除后，前序遍历");
        binaryTree.preOrder();
    }
}

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");
        }
    }

    //前序查找
    public HeroNode preOrederSearch(int no){
        if (root != null){
            return root.preOrderSearch(no);
        }else {
            return null;
        }
    }
    //中序查找
    public HeroNode infixOrderSeach(int no){
        if (root != null){
            return root.infixOrderSearch(no);
        }else {
            return null;
        }
    }
    //后序查找
    public HeroNode postOrderSeach(int no){
        if (root != null){
            return root.postOrderSearch(no);
        }else {
            return null;
        }
    }

    //删除节点
    public void delNode(int no){
        if (root != null){//判断root是不是要删除的节点
            if (root.getNo() == no){
                root = null;
            }else {
                root.delNode(no);
            }
        }
    }

}
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();
        }
    }
    //编写中序遍历方法
    public void infixOrder(){

        //递归向左子树前序遍历
        if (this.left != null){
            this.left.infixOrder();
        }

        System.out.println(this);//输出父节点

        //递归向右子树前序遍历
        if (this.right != null){
            this.right.infixOrder();
        }
    }
    //编写后序遍历方法
    public void postOrder(){
        if (this.left != null){
            this.left.postOrder();
        }

        if (this.right != null){
            this.right.postOrder();
        }
        System.out.println(this);
    }
    public static int i = 1, j = 1, k =1;
    //编写前序查找方法
    public HeroNode preOrderSearch(int no){
        System.out.println("前序遍历"+(i++)+"次");
        if (this.no == no){
            return this;
        }
        HeroNode heroNode = null;
        if (this.left != null){
            heroNode = this.left.preOrderSearch(no);
        }
        //不等于空说明在左边找到了
        if (heroNode != null){
            return heroNode;
        }
        if (this.right != null){
            heroNode = this.right.preOrderSearch(no);
        }
        return heroNode;
    }

    //中序遍历查找
    public HeroNode infixOrderSearch(int no){

        HeroNode heroNode = null;
        //先判断当前节点的左子节点是否为空，不为空继续进行中序查找
        if (this.left != null){
            heroNode = this.left.infixOrderSearch(no);
        }
        if (heroNode != null){
            return heroNode;
        }
        System.out.println("中序遍历"+(j++)+"次");
        if (this.no == no){
            return this;
        }
        if (this.right != null){
            heroNode = this.right.infixOrderSearch(no);
        }

        return heroNode;
    }

    //后序遍历查找
    public HeroNode postOrderSearch(int no){

        HeroNode heroNode = null;
        //判断当前节点的左子节点是否为空，不为空，则递归后序遍历查找
        if (this.left != null){
            heroNode = this.left.postOrderSearch(no);
        }
        if (heroNode != null){
            return heroNode;
        }
        //判断当前节点的右子节点是否为空，不为空，则递归后序遍历查找
        if (this.right != null){
            heroNode = this.right.postOrderSearch(no);
        }
        if (heroNode != null){
            return heroNode;
        }
        System.out.println("后序遍历"+(k++)+"次");
        //左右子树都没有找到，比较当前节点是不是
        if (this.no == no){
            return this;
        }
        return heroNode;
    }

    //递归删除节点
    //规定：如果是叶子节点就删除节点，如果非叶子节点就删除子树
    public void delNode(int no){
        if (this.left !=null && this.left.no == no){
            this.left = null;
            return;
        }
        if (this.right != null && this.right.no == no){
            this.right = null;
            return;
        }
        if (this.left != null){
            this.left.delNode(no);
        }
        if (this.right != null){
            this.right.delNode(no);
        }

    }
}

来源：CSDN

作者：春_

链接：https://blog.csdn.net/weixin_43736084/article/details/104144986