Java 精炼解读数据结构的链表的概念与实现

//ListNode代表一个节点
 
class ListNode{
    public int val;
    public ListNode next;
 
    //构造方法
    public ListNode(int val){
        this.val = val;
    }
}

//MyLinkedList 代表这是一个链表
 
public class MyLinkedList {
    public ListNode head;//链表的头引用，所以定义在链表里，head是链表的头，不是节点的头，节点只有两个属性，一个属性是val值，一个属性是next值，所以不能定义在ListNode类里面
    ListNode listNode = new ListNode(2);//节点实例化，val域赋值为2
}

/MyLinkedList 代表这是一个链表
public class MyLinkedList {
    public ListNode head;//链表的头引用，所以定义在链表里
    public  void createList(){
        ListNode listNode0 = new ListNode(11);
        ListNode listNode1 = new ListNode(26);
        ListNode listNode2 = new ListNode(23);
        ListNode listNode3 = new ListNode(45);
        ListNode listNode4 = new ListNode(56);
        listNode0.next = listNode1;
        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        this.head = listNode0;
    }

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

 //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.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //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;
    }

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

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

public ListNode findIndex(int index){
        ListNode cur = this.head;
        while(index -1 != 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 || index > size()){
            System.out.println("位置不合法");
            return;
        }
            if(index == 0){
                addFirst(data);
                return;
            }
            if(index == size()){
                addLast(data);
                return;
            }
 
            ListNode cur = findIndex(index);
            ListNode node = new ListNode(data);
            node.next = cur.next;
            cur.next = node;
 
    }

//删除第一次出现关键字为key的节点
    public void remove(int key){
        if(this.head == null){
            System.out.println("没有你要删除的节");
            return;
        }
       if (this.head.val == key){
           this.head = this.head.next;
           return;
        }
       ListNode cur = this.head;
       while (cur.next != null){
           if(cur.next.val == key){
               cur.next = cur.next.next;
               return;
           }
           cur = cur.next;
       }
       if(cur.next == null){
           System.out.println("没有该节点");
           return;
       }
 
    }

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