【浅学Java数据结构】简单模拟实现双向链表

模拟实现：

public class DoubleLinkedList {
    static class ListNode{
        int data;
        ListNode next;
        ListNode prev;
        public ListNode(int val){
            this.data=val;
            this.next=null;
            this.prev=null;
        }
    }

    public ListNode head;//标记头
    public ListNode last;//标记尾

    //遍历打印链表
    public void display(){
        ListNode cur=this.head;
        while(cur!=null){
            System.out.print(cur.data+" ");
            cur=cur.next;
        }
        System.out.println();
    }

    //尾插法
    public void addLast(int val){
        ListNode node=new ListNode(val);
        if(this.head==null) {
            this.head = node;
            this.last = node;
        }else{
            this.last.next=node;
            node.prev=this.last;
            this.last=node;
        }
    }

    //头插法
    public void addFirst(int val){
        ListNode node=new ListNode(val);
        if(this.head==null) {
            this.head = node;
            this.last = node;
        }else{
            node.next=this.head;
            this.head.prev=node;
            this.head=node;
        }
    }

    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int val){
        ListNode node=new ListNode(val);
        ListNode cur=this.head;

        int count=0;
        while(cur!=null){
            cur=cur.next;
            count++;
        }
        if(index<0||index>count){
            throw new RuntimeException("下标不合理");
        }
        if(index==0){
            addFirst(val);
            return;
        }
        if(index==count){
            addLast(val);
            return;
        }

        cur=this.head;
        for(int i=0;i<index;i++){
            cur=cur.next;
        }
        cur.prev.next=node;
        node.prev=cur.prev;
        node.next=cur;
        cur.prev=node;
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        if(this.head==null){
            return false;
        }
        ListNode cur=this.head;
        while(cur!=null){
            if(cur.data==key){
                return true;
            }
        }
        return false;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key){
        ListNode newHead=new ListNode(-1);//设置一个虚头节点，就可以不用单独处理删除头节点的情况
        newHead.next=head;
        head.prev=newHead;
        ListNode cur=head;
        while(cur!=null){
            if(key==cur.data&&cur.next!=null){//当是中间结点时
                cur.prev.next=cur.next;
                cur.next.prev=cur.prev;
                head=newHead.next;
                break;
            }else if(key==cur.data&&cur.next==null){//当是尾结点时
                cur.prev.next=null;
                head=newHead.next;
                break;
            }
            cur=cur.next;
        }
    }
    //删除所有值为key的节点  之遍历链表一遍
    public void removeAll(int key){
        ListNode newHead=new ListNode(-1);//设置一个虚头节点，就可以不用单独处理删除头节点的情况
        newHead.next=head;
        head.prev=newHead;
        ListNode cur=head;
        while(cur!=null){
            if(key==cur.data&&cur.next!=null){//当是中间结点时
                cur.prev.next=cur.next;
                cur.next.prev=cur.prev;
                cur=cur.next;
            }else if(key==cur.data&&cur.next==null){//当是尾结点时
                cur.prev.next=null;
                cur=cur.next;
            }else{
                cur=cur.next;
            }
        }
        head=newHead.next;
    }
    //链表长度
    public int size(){
        ListNode cur=head;
        int len=0;
        while(cur!=null){
            len++;
            cur=cur.next;
        }
        return len;
    }
    //链表清空
    public void clear(){
        this.head=null;
    }
}

测试代码：

public class Test {
    public static void main(String[] args) {
        DoubleLinkedList linkedList = new DoubleLinkedList();
        linkedList.addLast(1);
        linkedList.addLast(1);
        linkedList.addLast(1);
        linkedList.addLast(2);
        linkedList.addLast(3);
        linkedList.addLast(4);
        linkedList.addLast(5);
        linkedList.display();

        linkedList.addIndex(0,10);
        linkedList.display();
        linkedList.addIndex(8,20);
        linkedList.display();
        linkedList.addIndex(4,30);
        linkedList.display();

        boolean flg=linkedList.contains(10);
        System.out.println(flg);

        linkedList.remove(10);
        linkedList.display();
        linkedList.remove(20);
        linkedList.display();
        linkedList.remove(30);
        linkedList.display();

        linkedList.removeAll(1);
        linkedList.display();

        int len=linkedList.size();
        System.out.println(len);

        linkedList.clear();
    }
}

运行结果：