数据结构: 树

  树存储方式能提高数据存储,读取的效率.

二叉树: 

 

二叉树的遍历

  前序遍历: 先输出父节点,再遍历左子树和右子树。

  中序遍历: 先遍历左子树,再输出父节点, 再遍历右子树。

  后序遍历: 先遍历左子树,再遍历右子树, 最后输出父节点。

public class BinaryTreeDemo {
    public static void main(String[] args) {
        // 先创建一棵二叉树
        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");

        binaryTree.setRoot(root);
        root.setLeft(node2);
        root.setRight(node3);
        node3.setRight(node4);
        node3.setLeft(node5);

        // 前序遍历
        System.out.println("前序遍历");
        binaryTree.preOrder();
        binaryTree.delNode(3);
        System.out.println("删除后:");
        binaryTree.preOrder();
        //HeroNode nodeT = binaryTree.preOrderSearch(5);
        //System.out.println(nodeT);
        //BinaryTree.printCount();

        HeroNode.count = 0;
        // 中序遍历
        //System.out.println("中序遍历");
        //binaryTree.infixOrder();
        //nodeT = binaryTree.infixOrderSearch(5);
        //System.out.println(nodeT);
        //BinaryTree.printCount();

        HeroNode.count = 0;
        // 后序遍历
        //System.out.println("后序遍历");
        //binaryTree.postOrder();
//        nodeT = binaryTree.postOrderSearch(5);
//        System.out.println(nodeT);
//        BinaryTree.printCount();
    }
}

class BinaryTree{
    private HeroNode root;

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

    public void delNode(int no){
        if(this.root == null){
            System.out.println("二叉树为空");
        }else if(this.root != null && this.root.getNo() == no){
            this.root = null;
        }else{
            this.root.delNode(no);
        }
    }

    // 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");
        }
    }

    // 前序遍历查找
    public HeroNode preOrderSearch(int no){
        if(this.root != null){
            return this.root.preOrderSearch(no);
        }else{
            System.out.println("二叉树为空,无法遍历");
            return null;
        }
    }

    // 中序遍历查找
    public HeroNode infixOrderSearch(int no){
        if(this.root != null){
            return this.root.infixOrderSearch(no);
        }else{
            System.out.println("二叉树为空,无法遍历");
            return null;
        }
    }

    // 后序遍历查找
    public HeroNode postOrderSearch(int no){
        if(this.root != null){
            return this.root.postOrderSearch(no);
        }else{
            System.out.println("二叉树为空,无法遍历");
            return null;
        }
    }

    public static void printCount(){
        HeroNode.printCount();
    }
}

class HeroNode{
    public static int count = 0;
    private int no;
    private String name;
    private HeroNode left; // 默认为null
    private HeroNode right; // 默认为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 + '\'' +
                '}';
    }

    // 递归删除结点
    public void delNode(int no){

        if(this.left != null){
            if(this.left.no == no){
                this.left = null;
                return;
            }else{
                this.left.delNode(no);
            }
        }

        if(this.right != null){
            if(this.right.no == no){
                this.right = null;
                return;
            }else{
                this.right.delNode(no);
            }
        }
    }

    // 前序遍历
    public void preOrder(){
        System.out.println(this); // 先输出父结点
        // 递归左子树
        if(null != this.left){
            this.left.preOrder();
        }

        // 递归右子树
        if(null != this.right){
            this.right.preOrder();
        }
    }

    // 中序遍历
    public void infixOrder(){

        // 先递归左子树
        if(null != this.left){
            this.left.infixOrder();
        }

        System.out.println(this); // 输出父结点

        // 最后递归右子树
        if(null != this.right){
            this.right.infixOrder();
        }
    }

    // 后序遍历
    public void postOrder(){

        // 先递归左子树
        if(null != this.left){
            this.left.postOrder();
        }

        // 再递归右子树
        if(null != this.right){
            this.right.postOrder();
        }

        System.out.println(this); // 最后输出父结点
    }

    // 前序遍历查找
    public HeroNode preOrderSearch(int no){
        count++;
        HeroNode node = null;
        if(this.no == no){
            return this;
        }

        if(this.left != null){
            node = this.left.preOrderSearch(no);
        }

        if(null != node){
            return node;
        }

        if(this.right != null){
            node = this.right.preOrderSearch(no);
        }

        return node;
    }

    // 中序遍历查找
    public HeroNode infixOrderSearch(int no){
        HeroNode node = null;

        if(this.left != null){
            node = this.left.infixOrderSearch(no);
        }

        if(null != node){
            return node;
        }

        count++;
        if(this.no == no){
            return this;
        }

        if(this.right != null){
            node = this.right.infixOrderSearch(no);
        }

        return node;
    }

    // 后序遍历查找
    public HeroNode postOrderSearch(int no){
        HeroNode node = null;

        if(this.left != null){
            node = this.left.postOrderSearch(no);
        }

        if(null != node){
            return node;
        }

        if(this.right != null){
            node = this.right.postOrderSearch(no);
        }

        if(null != node){
            return node;
        }

        count++;
        if(this.no == no){
            return this;
        }

        return node;
    }

    public static void printCount(){
        System.out.printf("遍历了%d次\n",count);
    }
}