第三章 线性表2（链接表）

3.5.2 链接表接口

链接表可以看成是一组结点序列以及基于结点进行操作的线性结果的抽象，或则说是对链表的抽象。

链接表的接口：

package com.datastructure.chapter03.interfaces;

import com.datastructure.chapter03.exception.InvalidNodeException;
import com.datastructure.chapter03.exception.OutOfBoundaryException;

/** 
 * @ClassName: LinkedList 
 * @Description: 链接表接口
 * @author 
 * @date 2018年3月15日 下午9:18:35 
 *  
 */
public interface LinkedList {
    //查询链接表当前的规模
    public int getSize();
    
    //判断列表是否为空
    public boolean isEmpty();
    
    //返回第一个结点
    public Node first() throws OutOfBoundaryException;
    
    //返回最后一个结点
    public Node last() throws OutOfBoundaryException;
    
    //返回p之后的结点
    public Node getNext(Node p) throws InvalidNodeException,OutOfBoundaryException;
    
    //返回p之前的结点
    public Node getPre(Node p) throws InvalidNodeException,OutOfBoundaryException;

    //将e作为第一个元素插入链接表，并返回e所在结点
    public Node insertFirst(Object e);
    
    //将e作为最后一个元素插入列表，并返回e所在结点
    public Node insertLast(Object e);
    
    //将e插入至p之后的位置，并返回e所在结点
    public Node insertAfter(Node p,Object e) throws InvalidNodeException;
    
    //将e插入至p之前的位置，并返回e所在结点
    public Node insertBefore(Node p) throws InvalidNodeException;
    
    //删除首元素，并返回之
    public Object remove(Node p) throws InvalidNodeException;
    
    //删除首元素，并返回之
    public Object removeFirst() throws InvalidNodeException;
    
    //删除末元素，并返回之
    public Object removeLast() throws OutOfBoundaryException;
    
    //将处于给定位置的元素替换为新元素，并返回被替换的元素
    public Object replace(Node p,Object e) throws InvalidNodeException;
    
    //元素迭代器
    public Iterateor elements();
    
    
}

其中迭代器Iterator的接口：

package com.datastructure.chapter03.interfaces;

/** 
 * @ClassName: Iterateor 
 * @Description: 迭代器
 * @author 
 * @date 2018年3月15日 下午9:35:16 
 *  
 */
public interface Iterateor {
    
    //移动到第一个元素
    public void first();
    
    //移动到下一个元素
    public void next();
    
    //检查迭代器中是否还有剩余的元素
    public boolean isDone();
    
    //返回当前元素
    public Object currentItem();
    
}

还有一个异常类InvalidNodeException：

package com.datastructure.chapter03.exception;

/** 
 * @ClassName: InvalidNodeException 
 * @Description: 
 * 产生这个异常：
 * 结点p==null
 * p在链接表中不存在
 * 在调用getPre(p),p已经是第一个存有数据的结点
 * 在调用getNext(p),p已经是最后一个存有数据的结点
 * @author 
 * @date 2018年3月15日 下午9:40:44 
 *  
 */
@SuppressWarnings("serial")
public class InvalidNodeException extends RuntimeException {
    
    public InvalidNodeException(String err){
        super(err);
    }
}

 

基于双向链表思想的链接表

package com.datastructure.chapter03.interfacesImpl;

import com.datastructure.chapter03.exception.InvalidNodeException;
import com.datastructure.chapter03.exception.OutOfBoundaryException;
import com.datastructure.chapter03.interfaces.Iterater;
import com.datastructure.chapter03.interfaces.LinkedList;
import com.datastructure.chapter03.interfaces.Node;

/** 
 * @ClassName: LinkedListDLNode 
 * @Description: 基于双向链表实现的链接表
 * @author mao
 * @date 2018年3月15日 下午9:53:07 
 *  
 */
public class LinkedListDLNode implements LinkedList {

    private int size; //规模
    
    private DLNode head;//头节点，哑元节点
    
    private DLNode tail;//尾节点，哑元节点
    
    public LinkedListDLNode() {
        size = 0;
        head = new DLNode();
        tail = new DLNode();
        head.setNext(tail);
        tail.setPre(head);
    }
    
    /* (非 Javadoc) 
     * <p>Title: getSize</p> 
     * <p>Description: 查询链接表当前的规模</p> 
     * @return 
     * @see com.datastructure.chapter03.interfaces.LinkedList#getSize() 
     */
    @Override
    public int getSize() {
        return size;
    }

    /* (非 Javadoc) 
     * <p>Title: isEmpty</p> 
     * <p>Description: 判断链接表是否为空</p> 
     * @return 
     * @see com.datastructure.chapter03.interfaces.LinkedList#isEmpty() 
     */
    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    /* (非 Javadoc) 
     * <p>Title: first</p> 
     * <p>Description: 返回第一个结点</p> 
     * @return
     * @throws OutOfBoundaryException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#first() 
     */
    @Override
    public Node first() throws OutOfBoundaryException {
        if(isEmpty())
            throw new OutOfBoundaryException("错误，链接表为空!");
        return head.getNext();
    }

    /* (非 Javadoc) 
     * <p>Title: last</p> 
     * <p>Description: 返回最后一个结点</p> 
     * @return
     * @throws OutOfBoundaryException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#last() 
     */
    @Override
    public Node last() throws OutOfBoundaryException {
        if(isEmpty())
            throw new OutOfBoundaryException("错误，链接表为空!");
        return tail.getPre();
    }

    /* (非 Javadoc) 
     * <p>Title: getNext</p> 
     * <p>Description: 返回p之后的结点</p> 
     * @param p
     * @return
     * @throws InvalidNodeException
     * @throws OutOfBoundaryException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#getNext(com.datastructure.chapter03.interfaces.Node) 
     */
    @Override
    public Node getNext(Node p) throws InvalidNodeException,
            OutOfBoundaryException {
        DLNode node = checkPosition(p);
        node = node.getNext();
        if(node == tail)
            throw new OutOfBoundaryException("错误：已经是链接表尾端。");
        return node;
    }

    

    /* (非 Javadoc) 
     * <p>Title: getPre</p> 
     * <p>Description: 返回p之前的结点</p> 
     * @param p
     * @return
     * @throws InvalidNodeException
     * @throws OutOfBoundaryException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#getPre(com.datastructure.chapter03.interfaces.Node) 
     */
    @Override
    public Node getPre(Node p) throws InvalidNodeException,
            OutOfBoundaryException {
        DLNode node = checkPosition(p);
        node = node.getPre();
        if(node == head)
            throw new OutOfBoundaryException("错误：已经是链接表前端。");
        return node;
    }

    /* (非 Javadoc) 
     * <p>Title: insertFirst</p> 
     * <p>Description: 将e作为第一个元素插入链接表</p> 
     * @param e
     * @return 
     * @see com.datastructure.chapter03.interfaces.LinkedList#insertFirst(java.lang.Object) 
     */
    @Override
    public Node insertFirst(Object e) {
        
        DLNode node = new DLNode(e, head, head.getNext());
        head.getNext().setPre(node);
        head.setNext(node);
        size++;
        return node;
    }

    @Override
    public Node insertLast(Object e) {
        DLNode node = new DLNode(e, tail.getPre(), tail);
        tail.getPre().setNext(node);
        tail.setPre(node);
        size++;
        return node;
    }

    /* (非 Javadoc) 
     * <p>Title: insertAfter</p> 
     * <p>Description: 将e插入至p之后的位置，并返回e所在结点</p> 
     * @param p
     * @param e
     * @return
     * @throws InvalidNodeException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#insertAfter(com.datastructure.chapter03.interfaces.Node, java.lang.Object) 
     */
    @Override
    public Node insertAfter(Node p, Object e) throws InvalidNodeException {
        
        DLNode node = checkPosition(p);
        DLNode newNode = new DLNode(e, node, node.getNext());
        node.getNext().setPre(newNode);
        node.setNext(newNode);
        size++;
        return newNode;
    }

    /* (非 Javadoc) 
     * <p>Title: insertBefore</p> 
     * <p>Description: 将e插入p之前，并返回e所在结点</p> 
     * @param p
     * @param e
     * @return
     * @throws InvalidNodeException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#insertBefore(com.datastructure.chapter03.interfaces.Node, java.lang.Object) 
     */
    @Override
    public Node insertBefore(Node p,Object e) throws InvalidNodeException {
        DLNode node = checkPosition(p);
        DLNode newNode = new DLNode(e,node.getPre(),node);
        node.setPre(newNode);
        node.getPre().setNext(newNode);
        size++;
        return newNode;
    }

    /* (非 Javadoc) 
     * <p>Title: remove</p> 
     * <p>Description: 删除给定位置处元素，并返回之</p> 
     * @param p
     * @return
     * @throws InvalidNodeException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#remove(com.datastructure.chapter03.interfaces.Node) 
     */
    @Override
    public Object remove(Node p) throws InvalidNodeException {
        DLNode node = checkPosition(p);
        Object obj = node.getData();
        node.getPre().setNext(node.getNext());
        node.getNext().setPre(node.getPre());
        size--;
        return obj;
    }

    
    /* (非 Javadoc) 
     * <p>Title: removeFirst</p> 
     * <p>Description: 移除第一个结点</p> 
     * @return
     * @throws InvalidNodeException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#removeFirst() 
     */
    @Override
    public Object removeFirst() throws InvalidNodeException {
        return remove(head.getNext());
    }

    /* (非 Javadoc) 
     * <p>Title: removeLast</p> 
     * <p>Description: 移除最后一个结点</p> 
     * @return
     * @throws OutOfBoundaryException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#removeLast() 
     */
    @Override
    public Object removeLast() throws OutOfBoundaryException {
        return remove(tail.getPre());
    }

    /* (非 Javadoc) 
     * <p>Title: replace</p> 
     * <p>Description: 将处于给定位置元素替换为新元素，并返回被替换的元素</p> 
     * @param p
     * @param e
     * @return
     * @throws InvalidNodeException 
     * @see com.datastructure.chapter03.interfaces.LinkedList#replace(com.datastructure.chapter03.interfaces.Node, java.lang.Object) 
     */
    @Override
    public Object replace(Node p, Object e) throws InvalidNodeException {
        DLNode node = checkPosition(p);
        Object obj = node.getData();
        node.setData(e);
        return obj;
    }

    @Override
    public Iterater elements() {
        return new LinkedListIterator(this);
    }
    
    /** 
     * @Title: checkPosition 
     * @Description:  判断p是否合法，合法则转换为DLNode
     * @param @param p
     * @param @return
     * @param @throws InvalidNodeException  
     * @return DLNode   
     * @throws 
     */
    protected DLNode checkPosition(Node p) throws InvalidNodeException{
        if(null == p)
            throw new InvalidNodeException("错误：p为空。");
        if(p == head)
            throw new InvalidNodeException("错误：p指向头结点，非法。");
        if(p == tail)
            throw new InvalidNodeException("错误：p指向尾节点，非法。");
        DLNode node = (DLNode) p;
        return node;
    }

}

迭代器的实现类：

package com.datastructure.chapter03.interfacesImpl;

import com.datastructure.chapter03.exception.OutOfBoundaryException;
import com.datastructure.chapter03.interfaces.Iterater;
import com.datastructure.chapter03.interfaces.LinkedList;
import com.datastructure.chapter03.interfaces.Node;

/** 
 * @ClassName: LinkedListIterator 
 * @Description: 链接表的迭代器
 * @author 
 * @date 2018年3月15日 下午10:39:29 
 *  
 */
public class LinkedListIterator implements Iterater {

    private LinkedList list;//链接表
    
    private Node current;//当前结点
    
    public LinkedListIterator(LinkedList list) {
        this.list = list;
        if(list.isEmpty())
            current = null;
        else
            current = list.first();
    }
    
    /* (非 Javadoc) 
     * <p>Title: first</p> 
     * <p>Description: 移动到第一个个元素</p>  
     * @see com.datastructure.chapter03.interfaces.Iterater#first() 
     */
    @Override
    public void first() {
        if(list.isEmpty())
            current = null;
        else
            current = list.first();
    }

    /* (非 Javadoc) 
     * <p>Title: next</p> 
     * <p>Description: 移动到下一个元素</p> 
     * @throws OutOfBoundaryException 
     * @see com.datastructure.chapter03.interfaces.Iterater#next() 
     */
    @Override
    public void next() throws OutOfBoundaryException{
        if(isDone())
            throw new OutOfBoundaryException("错误：已经没有元素。");
        if(current == list.last()) current = null;//当前元素后面没有更多元素
        else current = list.getNext(current);
        
    }

    /* (非 Javadoc) 
     * <p>Title: isDone</p> 
     * <p>Description:检查迭代器中是否还有剩余元素 </p> 
     * @return 
     * @see com.datastructure.chapter03.interfaces.Iterater#isDone() 
     */
    @Override
    public boolean isDone() {
        return current == null;
    }

    /* (非 Javadoc) 
     * <p>Title: currentItem</p> 
     * <p>Description: 返回当前元素</p> 
     * @return 
     * @see com.datastructure.chapter03.interfaces.Iterater#currentItem() 
     */
    @Override
    public Object currentItem() {
        if(isDone())
            throw new OutOfBoundaryException("错误：已经没有元素了");
        return current.getData();
    }

}