哈希表（Java）

哈希表基本介绍

散列表（Hash table，也叫哈希表），是根据关键码值(Keyvalue)而直接进行访问的数据结构。也就是说，它通过把关键码值映射到表中一个位置来访问记录，以加快查找的速度。这个映射函数叫做散列函数，存放记录的数组叫做散列表。

代码实现

首先编写一个存放节点的类

package com.athome.hashtab;

/**
 * Description:
 * Author:江洋大盗
 * Date:2021/1/21 16:12
 */
public class Hero {
    int id;//武将编号
    String name;//名字
    Hero next;

    public Hero(int id, String name) {
        this.id = id;
        this.name = name;
    }

    @Override
    public String toString() {
        return "武将{" +
                "姓名：" + name +
                ", 编号：" + id +
                '}';
    }
}

编写链表：

package com.athome.hashtab;

/**
 * Description:
 * Author:江洋大盗
 * Date:2021/1/21 16:10
 */
public class LinkedListHero {
    private Hero head = null;

    /**
     * 直接添加到链表最后
     *
     * @param hero 待添加的节点
     */
    public void add(Hero hero) {
        if (head == null) {
            head = hero;
            return;
        }
        Hero temp = head.next;
        while (temp != null) {
            temp = temp.next;
        }
        temp = hero;
    }

    /**
     * 按照武力值插入
     *
     * @param hero 待插入节点
     */
    public void addById(Hero hero) {
        if (head == null) {
            head = hero;
            return;
        }
        if (head.id > hero.id) {
            hero.next = head;
            head.next = hero;
            return;
        }
        Hero temp = head;
        while (temp.next != null) {
            if (temp.next.id > hero.id) {
                break;
            }
            temp = temp.next;
        }
        hero.next = temp.next;
        temp.next = hero;
    }

    /**
     * 删除节点
     *
     * @param id 待删除的编号
     */
    public void delHero(int id) {
        if (head == null) {
            return;
        }
        if (head.id == id) {
            head = head.next;
            return;
        }
        Hero temp = head;
        while (temp.next != null) {
            if (temp.id == id) {
                temp.next = temp.next.next;
                return;
            }
            temp = temp.next;
        }
        System.out.println("没有找到要删除的武将");
    }

    /**
     * @param id 待查找的武将编号
     * @return 返回查询结果，若没有找到返回null
     */
    public Hero find(int id) {
        if (head == null) {
            return null;
        }
        Hero temp = head;
        while (temp != null) {
            if (temp.id == id) {
                return temp;
            }
            temp = temp.next;
        }
        return null;
    }

    /**
     * 打印链表
     */
    public void list() {
        if (head == null) {
            return;
        }
        Hero temp = head;
        while (temp != null) {
            System.out.print("-->" + temp);
            temp = temp.next;
        }
        System.out.println();
    }

    /**
     * @return 如果链表为空，返回true,否则返回false
     */
    public boolean isEmpty() {
        return head == null;
    }
}

编写哈希表：

package com.athome.hashtab;

/**
 * Description:
 * Author:江洋大盗
 * Date:2021/1/21 17:04
 */
public class HashTable {
    private final int size;
    LinkedListHero[] listHeroes;

    public HashTable(int size) {
        this.size = size;
        listHeroes = new LinkedListHero[size];
        //初始化链表数组
        for (int i = 0; i < size; i++) {
            listHeroes[i] = new LinkedListHero();
        }
    }

    /**
     * @param power 武将武力值
     * @return 返回其所在的链表数组下标
     */
    private int HashCode(int power) {
        return power % size;
    }

    /**
     * 添加方法
     *
     * @param hero 待添加的英雄
     */
    public void add(Hero hero) {
        int hashCode = HashCode(hero.id);
        listHeroes[hashCode].addById(hero);
    }

    /**
     * @param id 待查找的武将编号
     */
    public void find(int id) {
        int hashCode = HashCode(id);
        Hero hero = listHeroes[hashCode].find(id);
        if (hero == null) {
            System.out.println("没有找到该武将");
        } else {
            System.out.println("您查找的武将为:" + hero);
        }
    }

    /**
     * 删除武将
     *
     * @param id 待删除的武将编号
     */
    public void delete(int id) {
        int hashCode = HashCode(id);
        listHeroes[hashCode].delHero(id);
    }

    /**
     * 打印链表
     */
    public void list() {
        for (int i = 0; i < size; i++) {
            if (listHeroes[i].isEmpty()) {
                System.out.println("第" + (i + 1) + "条链表为空。");
            } else {
                System.out.print("第" + (i + 1) + "条链表:");
                listHeroes[i].list();
            }
        }
    }
}

主方法测试：

package com.athome.hashtab;

import java.util.Scanner;

/**
 * Description:
 * Author:江洋大盗
 * Date:2021/1/21 17:25
 */
public class Demo {
    public static void main(String[] args) {
        String choose;
        HashTable hashTab = new HashTable(7);
        Scanner scanner = new Scanner(System.in);
        boolean loop = true;
        while (loop) {
            System.out.println("==========================");
            System.out.println("add:添加元素");
            System.out.println("list:打印元素");
            System.out.println("find:查找元素");
            System.out.println("delete:删除元素");
            System.out.println("exit:退出");
            System.out.print("请输入您的选择:");
            choose = scanner.next();
            switch (choose) {
                case "add":
                    System.out.print("请输入武将id:");
                    int id = scanner.nextInt();
                    System.out.print("请输入武将姓名:");
                    String name = scanner.next();
                    hashTab.add(new Hero(id, name));
                    break;
                case "list":
                    hashTab.list();
                    break;
                case "find":
                    System.out.print("请输入要查询的武将id:");
                    id = scanner.nextInt();
                    hashTab.find(id);
                    break;
                case "delete":
                    System.out.print("请输入要删除的武将id:");
                    id = scanner.nextInt();
                    hashTab.delete(id);
                    break;
                case "exit":
                    loop = false;
                    break;
            }
        }
    }
}

结语

只要能收获甜蜜，荆棘丛中也有蜜蜂忙碌的身影，未来的你一定会感谢现在努力的自己。