创建单向链表并计算节点数的Java程序

链表是一种线性数据结构。链表元素不存储在连续位置，元素使用指针链接。单向链表是节点的集合，每个节点有两部分，一个是数据，另一个是链接部分。

例子：

Input : AddNodes = {2, 3, 4}
Output: LinkedList = [2, 3, 4]
        Size = 3
        
Input : AddNodes = {1, 2, 3, 4, 5}
Output: LinkedList = [1, 2, 3, 4, 5]
        Size = 5

操作：

1. 创建节点链表
2. 定义 addNode()、displayNodes() 和 countNodes() 等方法
3. 得到最终答案

执行：

Java

// Java Program to Create a Singly Linked List
// of n Nodes and Count the Number of Nodes
import java.io.*;
import java.util.*;
 
public class LinkedListCreation {
 
    class Node {
        int data;
        Node next;
 
        // constructor to create new node
        Node(int data)
        {
            this.data = data;
            this.next = null;
        }
    }
 
    // Initially both head and tail are not
    // pointing to any other node
    Node head = null;
    Node tail = null;
 
    // method to add newNode in Linked List
    void addNode(int data)
    {
 
        Node newNode = new Node(data);
 
        // Checks if the list is empty
        if (head == null) {
            // If list is empty, both head and
            // tail will point to new node
            head = newNode;
            tail = newNode;
        }
        else {
 
            tail.next = newNode;
            // storing newnode in tail
            tail = newNode;
        }
    }
    // display linked list
    void displayNodes()
    {
 
        Node current = head;
        if (head == null) {
            System.out.println("Empty");
            return;
        }
        System.out.println("Nodes : ");
        while (current != null) {
 
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
 
    // method to count nodes
    int countNodes()
    {
        // Initially zero
        int count = 0;
 
        Node currentNode = head;
        // iterate until all the nodes are present
        while (currentNode != null) {
 
            count++;
            currentNode = currentNode.next;
        }
        // return the count
        return count;
    }
 
    public static void main(String[] args)
    {
 
        LinkedListCreation L1 = new LinkedListCreation();
 
        L1.addNode(1);
        L1.addNode(2);
        L1.addNode(3);
        L1.addNode(4);
 
        // Displays the nodes present in the list
        L1.displayNodes();
 
        // Counts the nodes present in the given list
        System.out.println("Total Nodes: "
                           + L1.countNodes());
    }
}

输出

Nodes : 
1 2 3 4 
Total Nodes: 4

新节点插入的时间复杂度：

1. 首先： O(1)
2. 最后： O(N)，其中 N 是链表的大小

时间复杂度对于计数节点数： O(N)，其中 N 是节点数