双向链表

 双向链表的操作：

查找；

增加；

删除；

package MyJava2;

public class DuLinkedList {
    private class Node{
        String data;
        Node prve;
        Node next;
        public Node(){}
        public Node(String data,Node prve,Node next){
            this.data=data;
            this.prve=prve;
            this.next=next;
        }
    }
    private Node header;
    private Node tail;
    private int size;

    public DuLinkedList(){//创建空链表
        header=null;
        tail=null;
    }
    public DuLinkedList(String data){//根据指定元素创建链表
        header=new Node(data,null,null);
        tail=header;
        size++;
    }

    public int len(){
        return size;
    }

    public String getData(int index){//根据索引获得元素
        return getNodeByIndex(index).data;
    }

    private Node getNodeByIndex(int index) {//根据索引获得指定节点
        if(index<0||index>size-1){
            throw new IndexOutOfBoundsException("OutOfIndex");
        }
        if(index<=size/2){
            Node current=header;
            for(int i=0;i<size/2&&current!=null;i++,current=current.next){
                if(i==index){
                    return current;
                }
            }
        }
        else {
            Node current=tail;
            for(int i=size-1;i>size/2&&current!=null;i--,current=current.next){
                if(i==index){
                    return current;
                }
            }
        }
        return null;
    }

    public int locate(String data){//获得指定元素的位置
        Node current=header;
        for(int i=0;i<size&&current!=null;i++,current=current.next){
            if(data.equals(current.data)){
                return i;
            }
        }return -1;
    }

    public void addAtTail(String data){//尾插
        if(header==null){
            header=new Node(data,null,null);
            tail=header;
        }else{
            Node newNode=new Node(data,tail,null);
            tail.next=newNode;
            tail=newNode;
        }size++;
    }
    public void addAtHeader(String data){//头插
        header=new Node(data,null,header);
        if(tail==null){//插入之前是空表
            tail=header;
        }
        size++;
    }

    public void add(String data,int index){//插入指定索引的元素
        if(index<0||index>size){
            throw new IndexOutOfBoundsException("OutOfIndex");
        }
        if(header==null){
            addAtTail(data);
        }else {
            if(index==0){
                addAtHeader(data);
            }else {
                Node prve=getNodeByIndex(index-1);
                Node next=prve.next;
                Node newNode=new Node(data,prve,next);
                prve.next=newNode;
                next.prve=newNode;
                size++;
            }
        }
    }

    public String delData(int index){//删除指定索引的元素
        if(index<0||index>size){
            throw new IndexOutOfBoundsException("OutOfIndex");
        }
        Node delNode=null;
        if(index==0){
            delNode=header;
            header=header.next;
            header.prve=null;
        }else {
            Node prve=getNodeByIndex(index-1);
            delNode=prve.next;
            prve.next=delNode.next;
            if(delNode.next!=null){
                delNode.next.prve=prve;
            }
            delNode.prve=null;
            delNode.next=null;
        }return delNode.data;
    }

    public String remove(){//删除最后的元素
        return delData(size-1);
    }

    public boolean empty(){
        return size==0;
    }

    public void clear(){
        header=null;
        tail=null;
        size=0;
    }

    public String toString(){
        StringBuffer sb=new StringBuffer();
        Node current=header;
        for(;current!=null;current=current.next){
            sb.append(current.data.toString()+",");
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        DuLinkedList d=new DuLinkedList();
        d.addAtHeader("B");
        d.add("A",0);
        d.addAtTail("C");
        System.out.println(d.toString());
        System.out.println(d.size);
        System.out.println(d.getNodeByIndex(2).data);
        d.delData(0);
        System.out.println(d.toString());
        System.out.println(d.empty());
    }
}