Java笔记：双向链表

双向链表

package DoubleList;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: GAOBO
 * Date: 2019-11-17
 * Time: 9:28
 */

public class DoubleList {
    class ListNode {
        public int data;
        public ListNode next;
        public ListNode prev;
        public ListNode(int data) {
            this.data = data;
        }
    }

    public ListNode head;
    public ListNode last;//尾巴

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

    //尾插法  又单独定义了一个尾
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if(this.head == null) {
            this.head = node;
            this.last = node;
        }else {
            this.last.next = node;
            node.prev = this.last;
            this.last = node;
        }
    }
    public void display(){
        ListNode cur = this.head;
        while (cur != null) {
            System.out.print(cur.data+" ");
            cur = cur.next;
        }
        System.out.println();
    }

    private ListNode searchIndex(int index) {
        if(index < 0 || index >= size()) {
            return null;
        }
        ListNode cur = this.head;
        while (index > 0) {
            cur = cur.next;
            index--;
        }
        return cur;
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index == 0) {
            addFirst(data);
            return ;
        }
        if(index == size()) {
            addLast(data);
            return ;
        }
        //中间插入
        ListNode node = new ListNode(data);
        ListNode cur = searchIndex(index);
        if(cur == null) {
            return ;
        }
		//改4个位置
        node.next =  cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }
    //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;
    }
    //查找是否包含关键字key是否在链表当中
    public boolean contains(int key){
        ListNode cur = this.head;
        while (cur != null) {
            if(cur.data == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public int remove(int key){
        ListNode cur = this.head;
        while (cur != null) {
            if(cur.data == key) {
				int oldData = cur.data;
                //3种情况
                if(cur == this.head) {
                    this.head = this.head.next;
                    this.head.prev = null;
                }else {
                    //中间位置和尾巴
                    cur.prev.next = cur.next;
                    if(cur.next != null) {
                        cur.next.prev = cur.prev;
                    }else {
                        this.last = cur.prev;
                    }
                }
                return oldData; 
            }
            cur = cur.next;
        }
		return -1;//循环结束都没有返回值，说明没有要删除的节点
    }
    //删除所有值为key的节点
   public void removeAllKey(int key){
       ListNode cur = this.head;
       while (cur != null) {
           if(cur.data == key) {
               //3种情况
               if(cur == this.head) {
                   this.head = this.head.next;
                   this.head.prev = null;
               }else {
                   //中间位置和尾巴
                   cur.prev.next = cur.next;
                   if(cur.next != null) {   //防止空指针异常
                       cur.next.prev = cur.prev; 
                   }else {
                       this.last = cur.prev;
                   }
               }
           }
           cur = cur.next;
       }
   }

   public void clear(){
        while (this.head != null) {
            ListNode cur = this.head.next;
            this.head.next = null;
            this.head.prev = null;
            this.head = cur;
            //cur = cur.next;
        }
        this.last = null;
   }


}