15.链地址法

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;
	}
}

 

转载于:https://my.oschina.net/helloXia/blog/1922548