双向链表

Posted 2022-12-09 ssdut_yrp

public class Link 
    public long dData;
    public Link next;
    public Link previous;

    public Link(long dData)
        this.dData=dData;
    

    public void displayLink()
        System.out.print(dData+" ");
    

public class DoubleLinkedList 
    private Link first;
    private Link last;

    public DoubleLinkedList()
        first=null;
        last=null;
    

    public boolean isEmpty()
        return (first==null);
    

    public void insertFirst(long dd)
        Link newLink = new Link(dd);
        if(isEmpty())
            last=newLink;
        else
            first.previous=newLink;
        
        newLink.next=first;
        first=newLink;
    

    public void insertLast(long dd)
        Link newLink=new Link(dd);
        if(isEmpty())
            first=newLink;
        
        else
            last.next=newLink;
            newLink.previous=last;
        
        last=newLink;
    

    public Link deleteFirst()//delete first link
        Link temp =first;
        if(first.next==null)//if only one items
            last=null;
        else
            first.next.previous=null;
        
        first=first.next;
        return temp;
    

    public Link deleteLast()//delete last link
        Link temp =last;
        if(first.next==null)//if only one items
            first=null;
        else
            last.previous.next=null;
        
        last=last.previous;
        return temp;
    

    public boolean insertAfter(long key,long dd)
        Link current =first;
        while(current.dData!=key)
            current=current.next;
            if(current==null)
                return false;//didn't find it 
            
        
        Link newLink = new Link(dd);
        if(current==last)
            newLink.next=null;
            last=newLink;
        
        else
            newLink.next=current.next;
            current.next.previous=newLink;
        
        newLink.previous=current;
        current.next=newLink;
        return true;
    

    public Link deleteKey(long key)
        Link current =first;
        while(current.dData!=key)
            current=current.next;
            if(current==null)
                return null;
        
        if(current==first)
            first=current.next;
        
        else
            current.previous.next=current.next;
        
        if(current==last)
            last=current.previous;
        
        else
            current.next.previous=current.previous;
        
        return current;
    

    public void displayForward()
        Link current=first;
        while(current!=null)
            current.displayLink();
            current=current.next;
        
        System.out.println("");
    
    //遍历
    public void displayBackward()
        Link current = last;//start at end
        while(current!=null)
            current.displayLink();
            current=current.previous;
        
        System.out.println("");
    
    //insertAfter在某一特定元素后面插入

public class DoubleLinkedApp 

    /**
     * @param args
     */
    public static void main(String[] args) 
        // TODO Auto-generated method stub
        DoubleLinkedList theList = new DoubleLinkedList();
        theList.insertFirst(22);
        theList.insertFirst(44);
        theList.insertFirst(66);
        theList.insertLast(11);
        theList.insertLast(33);
        theList.insertLast(55);
        theList.displayForward();
        theList.displayBackward();
        theList.deleteFirst();
        theList.deleteLast();
        theList.displayForward();
        theList.insertAfter(22, 77);
        theList.insertAfter(33, 88);
        theList.displayForward();