用列表头实现哈希表链接的 Java 程序
一个哈希表是一个执行连接数组的数据结构，它是一个将键映射到其值的结构。它使用哈希函数来计算键的索引位置，也称为哈希代码。它将把键和值对存储在一个桶数组中，从这个桶中，可以很容易地在键的帮助下找到值。为了找到该值，将对该键进行哈希运算，其结果将给出该值所在的位置。
进场:
insert:要在哈希表中插入一个键，将对一个键进行简单的哈希运算，以找到它将要插入的位置，之后，该键将被插入列表的头部。
删除:只需在哈希函数的帮助下遍历列表，直到找到密钥，然后简单地从列表中删除该密钥
实施:
Java 语言(一种计算机语言，尤用于创建网站)
// Java program which implement Hash Tables chaining with
// List Heads
import java.util.Scanner;
public class TestHashTables {
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.println(
"***** Hash Table Implementation *****");
System.out.println("Enter size of hash table");
// create object of hash table
HashTablesExample table
= new HashTablesExample(sc.nextInt());
boolean exit = false;
// Perform HashTable operations
while (!exit) {
System.out.println(
"** Hash Table Operations **");
System.out.println("1\. insert ");
System.out.println("2\. remove");
System.out.println("3\. print hash table");
System.out.println("4\. get");
System.out.println("5\. clear");
System.out.println("6\. size");
int choice = sc.nextInt();
switch (choice) {
case 1:
System.out.println("Enter key and value");
String key = sc.next();
int value = sc.nextInt();
table.insert(key, value);
break;
case 2:
System.out.println("Enter key");
String key2 = sc.next();
table.remove(key2);
System.out.println(
"Removed Successfully...");
break;
case 3:
System.out.println(
"Key-value pairs in the hash table are : ");
table.printHashTable();
break;
case 4:
System.out.println("Enter key");
String key3 = sc.next();
System.out.println("Key = " + key3
+ " Value = "
+ table.get(key3));
break;
case 5:
table.makeEmpty();
System.out.println(
"Hash Table Cleared Successfully..");
break;
case 6:
System.out.println("Size of the table is = "
+ table.getSize());
break;
default:
exit = true;
System.out.println(
"Exited Successfully...");
}
}
sc.close();
}
}
class HashTablesExample {
// class linked hash
class LinkedHash {
String key;
int value;
LinkedHash next;
// constructor of linked hash
LinkedHash(String key, int value)
{
this.key = key;
this.value = value;
this.next = null;
}
}
private int tableSize;
private int size;
private LinkedHash[] table;
// constructor of HashTableExample
public HashTablesExample(int ts)
{
size = 0;
tableSize = ts;
table = new LinkedHash[tableSize];
// initializing the hash table with null values
for (int i = 0; i < tableSize; i++)
table[i] = null;
}
// method to get the number of key-value pairs in the
// hash table
public int getSize() { return size; }
// method to clear the hash table entry
public void makeEmpty()
{
for (int i = 0; i < tableSize; i++)
table[i] = null;
}
// method to get value of a key
public int get(String key)
{
int value = (myhash(key) % tableSize);
if (table[value] == null)
return -1;
else {
LinkedHash current = table[value];
while (current != null
&& !current.key.equals(key)) {
current = current.next;
}
if (current == null) {
return -1;
}
else {
return current.value;
}
}
}
// method to insert a value in a hash table
public void insert(String key, int value)
{
int hash = (myhash(key) % tableSize);
if (table[hash] == null) {
table[hash] = new LinkedHash(key, value);
}
else {
LinkedHash entry = table[hash];
while (entry.next != null
&& !entry.key.equals(key)) {
entry = entry.next;
}
if (entry.key.equals(key)) {
entry.value = value;
}
else {
entry.next = new LinkedHash(key, value);
}
}
size++;
}
// method to remove the value with the specified key
public void remove(String key)
{
int value = (myhash(key) % tableSize);
if (table[value] != null) {
LinkedHash prev = null;
LinkedHash current = table[value];
while (current.next != null
&& !current.key.equals(key)) {
prev = current;
current = current.next;
}
if (current.key.equals(key)) {
if (prev == null) {
table[value] = current.next;
}
else {
prev.next = current.next;
}
size--;
}
}
}
// method which gives a hash value from a given
// specified string
private int myhash(String x)
{
int value = x.hashCode();
value %= tableSize;
if (value < 0) {
value = value + tableSize;
}
return value;
}
// method to print the value of hash table
public void printHashTable()
{
for (int i = 0; i < tableSize; i++) {
LinkedHash current = table[i];
while (current != null) {
System.out.println(
"Value = " + current.value + " "
+ "Key = " + current.key);
current = current.next;
}
}
System.out.println();
}
}
输出:
插入哈希表
从哈希表中删除
打印哈希表的键值对
从指定的键中获取值
清除哈希表
哈希表的大小
版权属于：月萌API www.moonapi.com，转载请注明出处
