同样是为了解决哈希表中索引重复问题的算法,基本思路为将哈希表中维护的数组改成存储链表的数组,将数据存在链表中。也可以用数组但是数组的插入和删除的效率较低,故采用链表。
实现:
链表的实现:
/*
* 链结点,相当于是车厢
*/
public class Node {
//数据域
public Info info;
//指针域
public Node next;
public Node(Info info) {
this.info = info;
}
}
/*
* 链表,相当于火车
*/
public class LinkList {
//头结点
private Node first;
public LinkList() {
first = null;
}
/**
* 插入一个结点,在头结点后进行插入
*/
public void insertFirst(Info info) {
Node node = new Node(info);
node.next = first;
first = node;
}
/**
* 删除一个结点,在头结点后进行删除
*/
public Node deleteFirst() {
Node tmp = first;
first = tmp.next;
return tmp;
}
/**
* 查找方法
*/
public Node find(String key) {
Node current = first;
while(!key.equals(current.info.getKey())) {
if(current.next == null) {
return null;
}
current = current.next;
}
return current;
}
/**
* 删除方法,根据数据域来进行删除
*/
public Node delete(String key) {
Node current = first;
Node previous = first;
while(!key.equals(current.info.getKey())) {
if(current.next == null) {
return null;
}
previous = current;
current = current.next;
}
if(current == first) {
first = first.next;
} else {
previous.next = current.next;
}
return current;
}
}
哈希表的实现:
public class HashTable {
private LinkList[] arr;
/**
* 默认的构造方法
*/
public HashTable() {
arr = new LinkList[100];
}
/**
* 指定数组初始化大小
*/
public HashTable(int maxSize) {
arr = new LinkList[maxSize];
}
/**
* 插入数据
*/
public void insert(Info info) {
//获得关键字
String key = info.getKey();
//关键字所自定的哈希数
int hashVal = hashCode(key);
if(arr[hashVal] == null) {
arr[hashVal] = new LinkList();
}
arr[hashVal].insertFirst(info);
}
/**
* 查找数据
*/
public Info find(String key) {
int hashVal = hashCode(key);
return arr[hashVal].find(key).info;
}
/**
* 删除数据
* @param key
* @return
*/
public Info delete(String key) {
int hashVal = hashCode(key);
return arr[hashVal].delete(key).info;
}
public int hashCode(String key) {
BigInteger hashVal = new BigInteger("0");
BigInteger pow27 = new BigInteger("1");
for(int i = key.length() - 1; i >= 0; i--) {
int letter = key.charAt(i) - 96;
BigInteger letterB = new BigInteger(String.valueOf(letter));
hashVal = hashVal.add(letterB.multiply(pow27));
pow27 = pow27.multiply(new BigInteger(String.valueOf(27)));
}
return hashVal.mod(new BigInteger(String.valueOf(arr.length))).intValue();
}
}
所存储的实体类:
/**
* 员工信息类
* @author Administrator
*
*/
public class Info {
private String key;
private String name;
public Info(String key, String name) {
this.key = key;
this.name = name;
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}