数据结构--哈希表（Java）

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介绍

哈希表 底层是 数组加链表 或者是 数组加二叉树 ，一个数组里面有多个链表，通过散列函数来提高效率

代码

package cn.guizimo.hashtab;

import java.util.Scanner;

/**
 * @author guizimo
 * @date 2020/7/23 10:29 下午
 */
public class HashTabDemo {
    public static void main(String[] args) {
        HashTab hashTab = new HashTab(7);
        String key = "";
        Scanner scanner = new Scanner(System.in);
        while (true){
            System.out.println("add:添加");
            System.out.println("list:显示");
            System.out.println("find:显示");
            System.out.println("exit:退出");
            key = scanner.next();
            switch (key){
                case "add":
                    System.out.println("输入id");
                    int id = scanner.nextInt();
                    System.out.println("输入名字");
                    String name =  scanner.next();
                    Emp emp = new Emp(id, name);
                    hashTab.add(emp);
                    break;
                case "list":
                   hashTab.list();
                   break;
                case "find":
                    System.out.println("请输入id");
                    id = scanner.nextInt();
                    hashTab.find(id);
                    break;
                case "exit":
                    scanner.close();
                    System.exit(0);
                default:
                    break;
            }
        }
    }
}

class Emp{
    public int id;
    public String name;
    public Emp next;

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

//哈希表
class HashTab{
    private EmpLinkedList[] empLinkedListArray;
    private int size;

    //构造器
    public HashTab(int size){
        this.size = size;
        empLinkedListArray = new EmpLinkedList[size];
        for (int i = 0; i < size; i++) {
            empLinkedListArray[i] = new EmpLinkedList();
        }
    }

    //添加
    public void add(Emp emp){
        int empLinkedListNo = hashFun(emp.id);
        empLinkedListArray[empLinkedListNo].add(emp);
    }

    public void find(int id){
        int empLinkedListNo = hashFun(id);
        Emp emp = empLinkedListArray[empLinkedListNo].find(id);
        if (emp != null){
            System.out.printf("在第%d条链表中找到id=%d\n",(empLinkedListNo+1),id);
        }else {
            System.out.println("没有找到");
        }
    }

    //遍历
    public void list(){
        for (int i = 0; i < size; i++) {
            empLinkedListArray[i].list(i);
        }
    }

    //散列(取模)
    public int hashFun(int id){
        return id % size;
    }
}

class EmpLinkedList{
    private Emp head;

    public void add(Emp emp){
        if(head == null){
            head = emp;
            return;
        }
        Emp curEmp = head;
        while (true){
            if(curEmp.next == null){
                break;
            }
            curEmp = curEmp.next;
        }
        curEmp.next = emp;
    }

    public void list(int no){
        if(head == null){
            System.out.println("第"+(no+1)+"条链表为空");
            return;
        }
        System.out.print("第"+(no+1)+"条链表信息");
        Emp curemp = head;
        while (true){
            System.out.printf("id=%d,name=%s\t",curemp.id,curemp.name);
            if(curemp.next == null){
                break;
            }
            curemp = curemp.next;
        }
        System.out.println();
    }

    public Emp find(int id){
        if(head == null){
            System.out.println("链表为空");
            return null;
        }
        Emp curEmp = head;
        while (true){
            if(curEmp.id == id){
                break;
            }
            if(curEmp.next == null){
                curEmp = null;
                break;
            }
            curEmp = curEmp.next;
        }
        return curEmp;
    }
}

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原文链接：https://www.cnblogs.com/guizimo/p/13369611.html

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