【Java数据结构】实现双链表

作者：渴望力量的土狗

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专栏：数据结构与算法

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MyLinkedList.java 

public class MyLinkedList {

    static  class ListNode{

        private int data;
        private ListNode next;
        private ListNode pre;
        public ListNode(){

        }

       public ListNode(int data) {
           this.data = data;

       }
   }

    ListNode head;
    ListNode tail;

    // 2、无头双向链表实现

        //头插法
        public  void addFirst(int data){

        ListNode node=new ListNode(data);

        if(this.head==null){
           this.head=node;
            this.tail=node;
        }else{
           node.next=this.head;
            head.pre=node;
            this.head=node;
        }

        }
        //尾插法
        public void addLast(int data){
            ListNode node=new ListNode(data);
            ListNode cur=this.tail;
            if(this.head==null){
                this.head=node;
                this.tail=node;
            }else{

                cur.next=node;
                node.pre=cur;
                this.tail=node;
            }



        }
        //任意位置插入,第一个数据节点为0号下标
        public boolean addIndex(int index,int data){
            ListNode node =new ListNode(data);

            if(index<0||index>size()){
                return false;
            }
            if(index==0){
                addFirst(data);
                return true;
            }
            if(index==size()){
                addLast(data);
                return true;
            }
            ListNode cur=this.head;
            if(index!=0){
                cur=cur.next;
                index--;
            }
            node.next=cur;
            cur.pre.next=node;
            node.pre=cur.pre;
            cur.pre=node;

            return true;

        }
        //查找是否包含关键字key是否在单链表当中
        public boolean contains(int key){
            ListNode cur=this.head;
            while (cur!=null){
                if(cur.data==key){
                    return true;
                }else {
                    cur=cur.next;
                }
            }
            return false;
        }
        //删除第一次出现关键字为key的节点
        public void remove(int key){
            if(this.head==null){
                return;
            }
            ListNode cur=this.head;
            while (cur!=null){
                if(cur.data==key){
                    if(this.head.data==key){
                        this.head=this.head.next;
                        if(head!=null){
                            head.pre=null;
                        }else{
                            this.tail=null;
                        }
                    }  else{
                        cur.pre.next=cur.next;
                        if(cur.next!=null){
                            cur.next.pre=cur.pre;
                        }else{
                            this.tail=cur.pre;
                        }

                    }

                    break;
                }else{
                    cur=cur.next;

                }
            }

        }
        //删除所有值为key的节点
        public void removeAllKey(int key){
            if(this.head==null){
                return;
            }
            ListNode cur=this.head;
            while (cur!=null){
                if(cur.data==key){
                    if(this.head.data==key){
                        this.head=this.head.next;
                        if(head!=null){
                            head.pre=null;
                        }else{
                            this.tail=null;
                        }
                    }  else{
                        cur.pre.next=cur.next;
                        if(cur.next!=null){
                            cur.next.pre=cur.pre;
                        }else{
                            this.tail=cur.pre;
                        }
                    }
                }
                    cur=cur.next;


            }



        }
        //得到单链表的长度
        public int size(){
            ListNode cur=this.head;
            int count=0;
            while(cur!=null){
                count++;
                cur=cur.next;
            }
            return count;

        }
        public void display(){

            ListNode cur=this.head;
            while(cur!=null){
                System.out.print(cur.data+" ");
                cur=cur.next;
            }
            System.out.println();

        }
        public void clear(){

            ListNode cur=this.head;
            while(cur!=null){
                ListNode curNext=cur.next;
                cur.pre=null;
                cur.next=null;
                cur=curNext;
            }

           this.head=null;
           this.tail=null;

        }

}

Test.java

public class Test {
    public static void main(String[] args) {
        MyLinkedList myLinkedList=new MyLinkedList();

        myLinkedList.addFirst(1);
        myLinkedList.addFirst(2);
        myLinkedList.addFirst(3);
        myLinkedList.display();
        System.out.println("==========================");
        myLinkedList.addLast(4);
        myLinkedList.addLast(5);
        myLinkedList.addLast(6);
        myLinkedList.display();
        System.out.println("====================");
        System.out.println(myLinkedList.size());
        System.out.println("==========================");
//        myLinkedList.clear();
//        myLinkedList.display();
          myLinkedList.remove(5);
          myLinkedList.display();
        System.out.println("=============================");
        System.out.println(myLinkedList.contains(6));
        System.out.println("=============================");
        myLinkedList.addLast(9);
        myLinkedList.addLast(9);
        myLinkedList.addLast(9);
        myLinkedList.display();
        System.out.println("=====================");
        myLinkedList.removeAllKey(9);
        myLinkedList.display();
        System.out.println("=======================");
        System.out.println(myLinkedList.addIndex(2, 8888));
        System.out.println(myLinkedList.addIndex(0, 6666));
        System.out.println(myLinkedList.addIndex(7, 168168));
        myLinkedList.display();


    }
}

测试结果：