SHA家族

1 package cn.smallmartial.hashTable;
  2 
  3 import java.util.HashMap;
  4 import java.util.Scanner;
  5 
  6 /**
  7  * @Author smallmartial
  8  * @Date 2019/6/13
  9  * @Email smallmarital@qq.com
 10  */
 11 public class HashTableDemo {
 12 
 13     public static void main(String[] args) {
 14         //创建hash表
 15         HashTab hashTab = new HashTab(7);
 16 
 17         //写一个简单的菜单
 18         String key = "";
 19         Scanner scanner = new Scanner(System.in);
 20         while(true) {
 21             System.out.println("add:  添加雇员");
 22             System.out.println("list: 显示雇员");
 23             System.out.println("find: 查找雇员");
 24             System.out.println("exit: 退出系统");
 25 
 26             key = scanner.next();
 27             switch (key) {
 28                 case "add":
 29                     System.out.println("输入id");
 30                     int id = scanner.nextInt();
 31                     System.out.println("输入名字");
 32                     String name = scanner.next();
 33                     //创建 雇员
 34                     Emp emp = new Emp(id, name);
 35                     hashTab.add(emp);
 36                     break;
 37                 case "list":
 38                     hashTab.list();
 39                     break;
 40                 case "find":
 41                     System.out.println("请输入要查找的id");
 42                     id = scanner.nextInt();
 43                     hashTab.findEmpById(id);
 44                     break;
 45                 case "exit":
 46                     scanner.close();
 47                     System.exit(0);
 48                 default:
 49                     break;
 50             }
 51         }
 52     }
 53 }
 54 //创建hashTab
 55 class HashTab{
 56     private  int size;
 57     private EmpLinkedList[] empLinkedListArray;
 58 
 59     public HashTab(int size) {
 60         this.size = size;
 61         empLinkedListArray = new EmpLinkedList[size];
 62 
 63         for (int i = 0; i < size; i++) {
 64              empLinkedListArray[i] = new EmpLinkedList();
 65         }
 66 
 67     }
 68 
 69     //添加雇员
 70     public void add(Emp emp){
 71         //根据员工ID 添加到哪条联
 72         int hashFun = hashFun(emp.id);
 73         empLinkedListArray[hashFun].add(emp);
 74 
 75     }
 76     
 77     //遍历链表
 78     public void list(){
 79         for (int i = 0; i < size; i++) {
 80             empLinkedListArray[i].list(i);
 81         }
 82     }
 83 
 84     //根据输入的id,查找雇员
 85     public void findEmpById(int id) {
 86         //使用散列函数确定到哪条链表查找
 87         int empLinkedListNO = hashFun(id);
 88         Emp emp = empLinkedListArray[empLinkedListNO].findEmpById(id);
 89         if(emp != null) {//找到
 90             System.out.printf("在第%d条链表中找到 雇员 id = %d\n", (empLinkedListNO + 1), id);
 91         }else{
 92             System.out.println("在哈希表中，没有找到该雇员~");
 93         }
 94     }
 95     public int hashFun(int id){
 96         return id % size;
 97     }
 98 }
 99 //表示雇员
100 class Emp {
101     public int id;
102     public String name;
103     public Emp next;
104 
105     public Emp(int id, String name) {
106         this.id = id;
107         this.name = name;
108     }
109 }
110 //表示链表
111 class EmpLinkedList{
112     private Emp head;
113 
114     public void add(Emp emp){
115         if (head == null){
116             head = emp;
117             return;
118         }
119 
120         Emp curEmp = head;
121         while (true){
122             if (curEmp.next == null){
123                 break;
124             }
125             curEmp = curEmp.next;
126         }
127         curEmp.next = emp;
128     }
129 
130     //遍历
131     public void list(int no){
132         if (head == null){
133             System.out.println("第"+no+"前链表为空");
134             return;
135         }
136         System.out.print("第"+no+"链表信息为：");
137         Emp curEmp = head;
138         while (true){
139             System.out.print(curEmp.id+"=>"+curEmp.name);
140             if (curEmp.next == null){
141                 break;
142             }
143             curEmp = curEmp.next;
144         }
145         System.out.println();
146     }
147 
148     //根据id查找雇员
149     //如果查找到，就返回Emp, 如果没有找到，就返回null
150     public Emp findEmpById(int id) {
151         //判断链表是否为空
152         if(head == null) {
153             System.out.println("链表为空");
154             return null;
155         }
156         //辅助指针
157         Emp curEmp = head;
158         while(true) {
159             if(curEmp.id == id) {//找到
160                 break;//这时curEmp就指向要查找的雇员
161             }
162             //退出
163             if(curEmp.next == null) {//说明遍历当前链表没有找到该雇员
164                 curEmp = null;
165                 break;
166             }
167             curEmp = curEmp.next;//以后
168         }
169 
170         return curEmp;
171     }
172 }