Java程序从循环链表的开头删除一个节点

在本文中，我们将学习如何从循环链表的开头删除节点。考虑如下所示的链表。

例子：

Input : 5->3->4->(head node)
Output: 3->4->(head node)

两个case同时解决问题，

情况一：列表为空

• 如果列表为空，我们将简单地返回。

情况二：列表不为空

• 定义一个代表节点的节点类。
• 删除（）：
  • 如果不存在节点，则从函数返回
  • 如果只有一个节点，则将 head 和 tail 都设置为 null
  • 如果它有多个节点，则删除前一个头节点，头将指向列表中的下一个节点，尾将指向新的头。
• printNode() 会将列表中存在的所有节点打印为：
  • 定义了指向头部的节点电流
  • 打印 current.val 直到它再次开始指向头部
  • 在每次迭代中，它将指向下一个节点

代码：

Java

// Java Program to Delete a Node From the Beginning of the
// Circular Linked List
  
public class Main {
  
    // Represents the node of list.
    public class Node {
        int val;
        Node next;
        public Node(int val) { this.val = val; }
    }
  
    // Initialising head and tail pointers
    public Node head = null;
    public Node tail = null;
  
    // add new node to the end
    public void addNode(int val)
    {
        // Creating new node
        Node node = new Node(val);
  
        // head and tail will point to new node
        // if list is empty
        if (head == null) {
            head = node;
            tail = node;
            node.next = head;
        }
  
        // otherwise tail point to new node and
        else {
            tail.next = node;
            tail = node;
            tail.next = head;
        }
    }
  
    // Deletes node from the beginning of the list
    public void delete()
    {
        // returns if list is empty
        if (head == null) {
            return;
        }
  
        // otherwise head will point to next element in the
        // list and tail will point to new head
        else {
            if (head != tail) {
                head = head.next;
                tail.next = head;
            }
  
            // if the list contains only one element
            // then both head and tail will point to null
            else {
                head = tail = null;
            }
        }
    }
  
    // displaying the nodes
    public void display()
    {
        Node current = head;
        if (head == null) {
            System.out.println("List is empty");
        }
        else {
            do {
                System.out.print(" " + current.val);
                current = current.next;
            } while (current != head);
            System.out.println();
        }
    }
  
    public static void main(String[] args)
    {
        Main list = new Main();
  
        // Adds data to the list
        list.addNode(5);
        list.addNode(3);
        list.addNode(4);
  
        // Printing original list
        System.out.println("Original List: ");
        list.display();
  
        // deleting node from beginning and
        // displaying the Updated list
        list.delete();
        System.out.println("Updated List: ");
        list.display();
    }
}

输出

Original List: 
 5 3 4
Updated List: 
 3 4