【算法与数据结构-java】哈希表实现员工信息的增删改查

视频来自B站尚硅谷韩顺平的Java数据结构与java算法教程的第88和第89p内容

地址：https://www.bilibili.com/video/BV1E4411H73v?p=89

在此基础上完成了课后习题：增加顺序添加员工及按Id删除员工的功能（没有涉及修改），相当于再复习一遍链表，完整代码如下，已本地运行：

package hashmap;

import java.util.Scanner;

public class HashTab {
    public static void main(String[] args){
        Hash hashTab = new Hash(7);
        String key = "";
        Scanner scanner = new Scanner(System.in);
        while (true){
            System.out.println("add:  添加雇员");
            System.out.println("list: 显示雇员");
            System.out.println("find: 查找雇员");
            System.out.println("del:  删除雇员");
            System.out.println("exit: 退出系统");
            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("请输入要查找的id");
                    id = scanner.nextInt();
                    hashTab.findEmpById(id);
                    break;
                case "del":
                    System.out.println("请输入要删除的id");
                    id = scanner.nextInt();
                    hashTab.delEmpById(id);
                    break;
                case "exit":
                    scanner.close();
                    System.exit(0);
                default:
                    break;
            }
        }

    }
}

class Hash{
    private EmpLinkedList[] empLinkedListArray;
    private int size;

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

    public void add(Emp emp){
        int empLinkedListNo = hashFun(emp.id);
        empLinkedListArray[empLinkedListNo].orderAdd(emp);
    }
    public void list(){
        for (int i = 0; i < size; i++){
            empLinkedListArray[i].list(i);
        }
    }

    public void findEmpById(int id){
        int empLinkedListNO = hashFun(id);
        Emp emp = empLinkedListArray[empLinkedListNO].findEmpById(id);
        if (emp != null){
            System.out.printf("在第%d条链表中找到该雇员，id=%d\n",(empLinkedListNO+1),id);
            System.out.println("该雇员的信息为:id= "+emp.id+" name= "+emp.name);
        }else {
            System.out.println("在哈希表中没有找到该雇员");
        }
    }

    public void delEmpById(int id){
        int empLinkedListNO = hashFun(id);
        empLinkedListArray[empLinkedListNO].delEmpById(id);
    }

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

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


class EmpLinkedList{
    private Emp head;
    public void add(Emp emp){
        //按顺序添加
        if(head == null){
            head = emp;
            return;
        }
        Emp curEmp = head;
        while (true){
            if(curEmp.next == null){
                break;
            }
            curEmp = curEmp.next;
        }
        curEmp.next = emp;
    }

    public void orderAdd(Emp emp){
        //按顺序添加员工信息
        if (head == null){
            //空链表
            head = emp;
            return;
        }
        if (head.id > emp.id){
            //如果头结点的id大于要插入的id，则将emp指向当前头结点，然后再把头结点置为emp
            emp.next = head;
            head = emp;
            return;
        }
        if (head.id == emp.id){
            //如果头结点的id等于要加入的id，则提示不能加入
            System.out.printf("第%d号员工已经存在，不能加人\n", emp.id);
            return;
        }
        Emp curEmp = head;
        boolean flag = false;
        while (true){
            if(curEmp.next == null){
                break;
            }
            if(curEmp.next.id > emp.id){
                break;
            }else if (curEmp.next.id == emp.id){
                flag = true;
                break;
            }
            curEmp = curEmp.next;//后移，遍历
        }
        if(flag){
            System.out.printf("第%d号员工已经存在，不能加人\n", emp.id);
        }else{
            if (curEmp.next == null){
                //如果当前链表只有一个节点，则直接添加到最后
                //head = emp;
                curEmp.next = emp;
            }else {
                //如果要插入的位置在节点中间
                emp.next = 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.println("第"+(no+1)+"条链表的信息为：");
        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 findEmpById(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;
    }

    public void delEmpById(int id){
        //按照id删除员工信息
        if (head == null){
            System.out.println("链表为空");
            return;
        }
        if (head.id == id) {
            // 如果头结点的id等于要删除的id，则将头结点指向下一个
            head = head.next;
            //head = null;
            return;
        }

        Emp curEmp = head;
        boolean flag = false;
        while (true) {
            if (curEmp.next == null) {
                break;
            }
            if (curEmp.next.id == id) {
                flag = true;
                break;
            }
            curEmp = curEmp.next;//后移，遍历
        }
        if (flag) {
            curEmp.next = curEmp.next.next;
        }else {
            System.out.println("没有找到第" + id + "号员工");
        }
    }
}