数据结构 玩转数据结构 12-2 AVL树计算高度及平衡因子

package com.company;

import java.util.ArrayList;

public class AVLTree<K extends Comparable<K>,V> {


    //1     定义Node
    class Node{
        private K key;
        private V value;
        private Node left,right;
        private int height;
        private int balanceFactor;

        public Node(K key, V value){
            this.key = key;
            this.value = value;
            this.left = null;
            this.right = null;
            this.height = 1;
        }

        @Override
        public String toString() {
            final StringBuffer sb = new StringBuffer("Node{");
            sb.append("key=").append(key);
            sb.append(", value=").append(value);
            sb.append('}');
            return sb.toString();
        }
    }

    //2     定义属性
    private int size;
    private Node root;

    /**
     * getHeight
     * @author weidoudou
     * @date 2023/4/1 11:34
     * @param node 请添加参数描述
     * @return int
     **/
    private int getHeight(Node node){
        if(null==node){
            return 0;
        }
        return node.height;
    }

    /**
     * getBalanceFactor
     * @author weidoudou
     * @date 2023/4/1 11:36
     * @param node 请添加参数描述
     * @return int
     **/
    private int getBalanceFactor(Node node){
        if(null==node){
            return 0;
        }
        return getHeight(node.left) - getHeight(node.right);
    }

    /**
     * 无参构造函数
     * @author weidoudou
     * @date 2023/1/1 11:09
     * @return null
     **/
    public AVLTree(){
        this.size = 0;
        this.root = null;
    }



    public boolean isEmpty() {
        return size==0?true:false;
    }

    public int getSize() {
        return size;
    }

    //3     定义包含函数
    private Node containsKey(K key,Node node){
        //结束条件
        if(null==node){
            return null;
        }

        //循环条件
        if(key.compareTo(node.key)<0){
            return containsKey(key,node.left);
        }else if(key.compareTo(node.key)>0){
            return containsKey(key, node.right);
        }else{//key.compareTo(node.key)=0 其实这个也是结束条件
            return node;
        }
    }

    public boolean contains(K key) {
        return containsKey(key,root)==null?false:true;
    }

    public V get(K key) {
        Node node = containsKey(key,root);
        if(null!=node){
            return node.value;
        }
        return null;
    }


    //3     递归，添加元素
    public void add(K key,V value,Node root){
        //3.1   终止条件
        //3.1.1 要插入的元素和二叉树原有节点相同,这个不用判断，因为已经调了containsKey方法判断了
        /*if(key.equals(root.e)){
            return;
        }*/

        //3.1.2 最终插入左孩子
        if(key.compareTo(root.key)<0 && root.left==null){
            root.left = new Node(key,value);
            size++;
            return;
        }

        //3.1.2 最终插入右孩子
        if(key.compareTo(root.key)>0 && root.right == null){
            root.right = new Node(key,value);
            size++;
            return;
        }

        //3.2   递归
        //3.2.1 递归左孩子
        if(key.compareTo(root.key)<0){
            add(key,value,root.left);
        }

        //3.2.2 递归右孩子
        if(key.compareTo(root.key)>0){
            add(key,value,root.right);
        }
        root.height = 1+Math.max(getHeight(root.left),getHeight(root.right));
        int balanceFactor = Math.abs(getBalanceFactor(root));
        if(balanceFactor>1){
            System.out.println("unbalanced:"+balanceFactor);
        }
    }

    public void add(K key, V value) {
        Node node = containsKey(key,root);
        //未找到，插值
        if(node==null){
            //2.1   考虑特殊情况,如果是第一次调用，root为null
            if(root==null){
                root = new Node(key,value);
                size++;
            }else{
                //2.2   添加递归方法
                add(key,value,root);
            }
        }else{
            node.value = value;
        }
        //找到后，更新值
    }

    public void set(K key, V value) {
        Node node = containsKey(key,root);
        if(node == null){
            throw new IllegalArgumentException("要修改的值不存在");
        }
        node.value = value;
    }

    private Node remove(Node node,K key){
        //终止条件1 基本判断不到，因为已经判断了containskey
        /*if(node==null){
            return null;
        }*/

        //递归
        if(key.compareTo(node.key)<0){
            node.left = remove(node.left,key);
            return node;
        }else if(key.compareTo(node.key)>0){
            node.right = remove(node.right,key);
            return node;
        }else{
            //已找到要删除的元素
            //1 如果只有左子节点或只有右子节点，则直接将子节点替换
            if(node.left==null){
                return node.right;
            }else if(node.right==null){
                return node.left;
            }else{
                //2 如果有左子节点和右子节点，则寻找前驱或后继 对当前节点替换掉
                Node nodeMain = findMin(node.right);
                nodeMain.right = removMin(node.right);//这块一箭双雕，既把后继节点问题解决了，也把后继删除了
                nodeMain.left = node.left;
                node.left = node.right = null;
                return node;
            }
        }
    }

    private Node findMin(Node node){
        //1     终止条件
        if(node.left==null){
            return node;
        }

        //2     递归
        return findMin(node.left);
    }

    private Node removMin(Node node){
        //终止条件
        if(node.left==null){
            Node rightNode = node.right;
            node.right = null;
            return rightNode;
        }

        //递归
        node.left = removMin(node.left);
        return node;
    }

    /**
     * 删除任意元素 若删除元素节点下只有一个节点直接接上即可，若有两个节点，则找前驱或后继，本节找前驱
     * @author weidoudou
     * @date 2023/1/1 11:52
     * @param key 请添加参数描述
     * @return V
     **/
    public V remove(K key) {
        Node node = containsKey(key,root);
        if(node == null){
            throw new IllegalArgumentException("要修改的值不存在");
        }
        size--;
        return remove(root, key).value;
    }

    public static void main(String[] args) {
        System.out.println("Pride and Prejudice");
        ArrayList<String> words = new ArrayList<>();

        if(FileOperation.readFile("pride-and-prejudice.txt",words)){
            System.out.println("Total words: "+words.size());
            AVLTree<String,Integer> avlTree = new AVLTree<>();
            for(String word:words){
                if(avlTree.contains(word)){
                    avlTree.set(word,avlTree.get(word)+1);
                }else{
                    avlTree.add(word,1);
                }
            }
            System.out.println("Total different words:"+avlTree.getSize());
        }


    }


}

package com.company;

import java.io.FileInputStream;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.Locale;
import java.io.File;
import java.io.BufferedInputStream;
import java.io.IOException;

// 文件相关操作
public class FileOperation {

    // 读取文件名称为filename中的内容，并将其中包含的所有词语放进words中
    public static boolean readFile(String filename, ArrayList<String> words){

        if (filename == null || words == null){
            System.out.println("filename is null or words is null");
            return false;
        }

        // 文件读取
        Scanner scanner;

        try {
            File file = new File(filename);
            if(file.exists()){
                FileInputStream fis = new FileInputStream(file);
                scanner = new Scanner(new BufferedInputStream(fis), "UTF-8");
                scanner.useLocale(Locale.ENGLISH);
            }
            else
                return false;
        }
        catch(IOException ioe){
            System.out.println("Cannot open " + filename);
            return false;
        }

        // 简单分词
        // 这个分词方式相对简陋, 没有考虑很多文本处理中的特殊问题
        // 在这里只做demo展示用
        if (scanner.hasNextLine()) {

            String contents = scanner.useDelimiter("\\A").next();

            int start = firstCharacterIndex(contents, 0);
            for (int i = start + 1; i <= contents.length(); )
                if (i == contents.length() || !Character.isLetter(contents.charAt(i))) {
                    String word = contents.substring(start, i).toLowerCase();
                    words.add(word);
                    start = firstCharacterIndex(contents, i);
                    i = start + 1;
                } else
                    i++;
        }

        return true;
    }

    // 寻找字符串s中，从start的位置开始的第一个字母字符的位置
    private static int firstCharacterIndex(String s, int start){

        for( int i = start ; i < s.length() ; i ++ )
            if( Character.isLetter(s.charAt(i)) )
                return i;
        return s.length();
    }
}

......
unbalanced:8
unbalanced:3
unbalanced:4
unbalanced:7
Total different words:6530
Class transformation time: 0.0195327s for 166 classes or 1.1766686746987952E-4s per class

Process finished with exit code 0