问：创建 N 个节点的双向链表并计算节点数的程序。

2025年3月17日 | 阅读 8 分钟

说明

在本程序中，我们将创建一个双向链表并计算列表中节点的数量。要计算节点数，我们通过递增计数器 1 来遍历列表。

Program to create a doubly linked list of n nodes and count the number of nodes

上面双向链表中存在的节点数为 5。

算法

定义一个 Node 类，它表示列表中的一个节点。它将有三个属性：数据、previous 指向前一个节点，以及 next 指向下一个节点。
定义另一个用于创建双向链表的类，它有两个节点：头节点和尾节点。最初，头节点和尾节点将指向 null。
addNode() 将向列表中添加节点。
1. 它首先检查头节点是否为 null，然后将节点作为头节点插入。
2. 头节点和尾节点都将指向新添加的节点。
3. Head 的前驱指针将指向 null，尾节点的后继指针将指向 null。
4. 如果头节点不为 null，则新节点将插入到列表的末尾，使得新节点的前一个指针将指向尾节点。
5. 新节点将成为新的尾节点。尾节点的下一个指针将指向 null。
countNodes() 函数将计算列表中存在的节点数。
1. 定义一个变量 counter 和一个指向头节点的新节点 current。
2. 遍历列表，通过将 current 节点指向列表中的下一个节点，直到 current 指向 null，来计算节点数。
3. 将计数器加 1。
display() 将显示列表中存在的所有节点。
1. 定义一个新节点“current”，它将指向头节点。
2. 打印 current.data 直到 current 指向 null。
3. 在每次迭代中，current 将指向列表中的下一个节点。

解决方案

Python

#Represent a node of doubly linked list
class Node:
    def __init__(self,data):
        self.data = data;
        self.previous = None;
        self.next = None;
        
class CountList:
    #Represent the head and tail of the doubly linked list
    def __init__(self):
        self.head = None;
        self.tail = None;
        
    #addNode() will add a node to the list
    def addNode(self, data):
        #Create a new node
        newNode = Node(data);
        
        #If list is empty
        if(self.head == None):
            #Both head and tail will point to newNode
            self.head = self.tail = newNode;
            #head's previous will point to None
            self.head.previous = None;
            #tail's next will point to None, as it is the last node of the list
            self.tail.next = None;
        else:
            #newNode will be added after tail such that tail's next will point to newNode
            self.tail.next = newNode;
            #newNode's previous will point to tail
            newNode.previous = self.tail;
            #newNode will become new tail
            self.tail = newNode;
            #As it is last node, tail's next will point to None
            self.tail.next = None;
            
    #countNodes() will count the nodes present in the list
    def countNodes(self):
        counter = 0;
        #Node current will point to head
        current = self.head;
        
        while(current != None):
            #Increment the counter by 1 for each node
            counter = counter + 1;
            current = current.next;
        return counter;
            
    #display() will print out the nodes of the list
    def display(self):
        #Node current will point to head
        current = self.head;
        if(self.head == None):
            print("List is empty");
            return;
        print("Nodes of doubly linked list: ");
        while(current != None): 
            #Prints each node by incrementing pointer.
            print(current.data),
            current = current.next;
            
dList = CountList();
#Add nodes to the list
dList.addNode(1);
dList.addNode(2);
dList.addNode(3);
dList.addNode(4);
dList.addNode(5);
 
#Displays the nodes present in the list
dList.display();
 
#Counts the nodes present in the given list
print("\nCount of nodes present in the list: " + str(dList.countNodes()));

输出

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

C

#include <stdio.h>
 
//Represent a node of the doubly linked list

struct node{
    int data;
    struct node *previous;
    struct node *next;
};    
 
//Represent the head and tail of the doubly linked list
struct node *head, *tail = NULL;
 
//addNode() will add a node to the list
void addNode(int data) {
    //Create a new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    
    //If list is empty
    if(head == NULL) {
        //Both head and tail will point to newNode
        head = tail = newNode;
        //head's previous will point to NULL
        head->previous = NULL;
        //tail's next will point to NULL, as it is the last node of the list
        tail->next = NULL;
    }
    else {
        //newNode will be added after tail such that tail's next will point to newNode
        tail->next = newNode;
        //newNode's previous will point to tail
        newNode->previous = tail;
        //newNode will become new tail
        tail = newNode;
        //As it is last node, tail's next will point to NULL
        tail->next = NULL;
    }
}
 
//countNodes() will count the nodes present in the list
int countNodes() {
    int counter = 0;
    //Node current will point to head
    struct node *current = head;
    
    while(current != NULL) {
        //Increment the counter by 1 for each node
        counter++;
        current = current->next;
    }
    return counter;
}
    
//display() will print out the nodes of the list
void display() {
    //Node current will point to head
    struct node *current = head;
    if(head == NULL) {
        printf("List is empty\n");
        return;
    }
    printf("Nodes of doubly linked list: \n");
    while(current != NULL) {
        //Prints each node by incrementing pointer.
        printf("%d ", current->data);
        current = current->next;
    }
}
 
int main()
{
    //Add nodes to the list
    addNode(1);
    addNode(2);
    addNode(3);
    addNode(4);
    addNode(5);
    
    //Displays the nodes present in the list
    display();
    
    //Counts the nodes present in the given list
    printf("\nCount of nodes present in the list: %d", countNodes());
 
    return 0;
}

输出

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

JAVA

public class CountList {
    
    //Represent a node of the doubly linked list

    class Node{
        int data;
        Node previous;
        Node next;
        
        public Node(int data) {
            this.data = data;
        }
    }
    
    //Represent the head and tail of the doubly linked list
    Node head, tail = null;
    
    //addNode() will add a node to the list
    public void addNode(int data) {
        //Create a new node
        Node newNode = new Node(data);
        
        //If list is empty
        if(head == null) {
            //Both head and tail will point to newNode
            head = tail = newNode;
            //head's previous will point to null
            head.previous = null;
            //tail's next will point to null, as it is the last node of the list
            tail.next = null;
        }
        else {
            //newNode will be added after tail such that tail's next will point to newNode
            tail.next = newNode;
            //newNode's previous will point to tail
            newNode.previous = tail;
            //newNode will become new tail
            tail = newNode;
            //As it is last node, tail's next will point to null
            tail.next = null;
        }
    }
    
    //countNodes() will count the nodes present in the list
    public int countNodes() {
        int counter = 0;
        //Node current will point to head
        Node current = head;
        
        while(current != null) {
            //Increment the counter by 1 for each node
            counter++;
            current = current.next;
        }
        return counter;
    }
    
    //display() will print out the elements of the list
    public void display() {
        //Node current will point to head
        Node current = head;
        if(head == null) {
            System.out.println("List is empty");
            return;
        }
        System.out.println("Nodes of doubly linked list: ");
        while(current != null) {
            //Prints each node by incrementing the pointer.

            System.out.print(current.data + " ");
            current = current.next;
        }
    }
    
    public static void main(String[] args) {
        
        CountList dList = new CountList();
        //Add nodes to the list
        dList.addNode(1);
        dList.addNode(2);
        dList.addNode(3);
        dList.addNode(4);
        dList.addNode(5);
        
        //Displays the nodes present in the list
        dList.display();
        
        //Counts the nodes present in the given list
        System.out.println("\nCount of nodes present in the list: " + dList.countNodes());
    }
}

输出

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

C#

using System; 
namespace DoublyLinkedList 
{                     
    public class Program
    {
        //Represent a node of the doubly linked list

        public class Node<T>{
            public T data;
            public Node<T> previous;
            public Node<T> next;
            
            public Node(T value) {
                data = value;
            }
        }
        
        public class CountList<T>{
            //Represent the head and tail of the doubly linked list
            protected Node<T> head = null;             
             protected Node<T> tail = null;
            
            //addNode() will add a node to the list
            public void addNode(T data) {
                //Create a new node
                Node<T> newNode = new Node<T>(data);
 
                //If list is empty
                if(head == null) {
                    //Both head and tail will point to newNode
                    head = tail = newNode;
                    //head's previous will point to null
                    head.previous = null;
                    //tail's next will point to null, as it is the last node of the list
                    tail.next = null;
                }
                else {
                    //newNode will be added after tail such that tail's next will point to newNode
                    tail.next = newNode;
                    //newNode's previous will point to tail
                    newNode.previous = tail;
                    //newNode will become new tail
                    tail = newNode;
                    //As it is last node, tail's next will point to null
                    tail.next = null;
                }
            }
            
            //countNodes() will count the nodes present in the list
            public int countNodes() {
                int counter = 0;
                //Node current will point to head
                Node<T> current = head;
 
                while(current != null) {
                    //Increment the counter by 1 for each node
                    counter++;
                    current = current.next;
                }
                return counter;
            }
            
            //display() will print out the nodes of the list
            public void display() {
                //Node current will point to head
                Node<T> current = head;
                if(head == null) {
                    Console.WriteLine("List is empty");
                    return;
                }
                Console.WriteLine("Nodes of doubly linked list: ");
                while(current != null) {
                    //Prints each node by incrementing the pointer.

                    Console.Write(current.data + " ");
                    current = current.next;
                }
            }
        }
        
        public static void Main()
        {
            CountList<int> dList = new CountList<int>();
            //Add nodes to the list
            dList.addNode(1);
            dList.addNode(2);
            dList.addNode(3);
            dList.addNode(4);
            dList.addNode(5);
 
            //Displays the nodes present in the list
            dList.display();
 
            //Counts the nodes present in the given list
            Console.WriteLine("\nCount of nodes present in the list: " + dList.countNodes());
        }    
    }
}

输出

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represent a node of doubly linked list
class Node{
    public $data;
    public $previous;
    public $next;
    
    function __construct($data){
        $this->data = $data;
    }
}
class CountList{
    //Represent the head and tail of the doubly linked list
    public $head;
    public $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    
    //addNode() will add a node to the list
    function addNode($data){
        //Create a new node
        $newNode = new Node($data);
        
        //If list is empty
        if($this->head == NULL) {
            //Both head and tail will point to newNode
            $this->head = $this->tail = $newNode;
            //head's previous will point to NULL
            $this->head->previous = NULL;
            //tail's next will point to NULL, as it is the last node of the list
            $this->tail->next = NULL;
        }
        else {
            //newNode will be added after tail such that tail's next will point to newNode
            $this->tail->next = $newNode;
            //newNode's previous will point to tail
            $newNode->previous = $this->tail;
            //newNode will become new tail
            $this->tail = $newNode;
            //As it is last node, tail's next will point to NULL
            $this->tail->next = NULL;
        }
    }
    
    //countNodes() will count the nodes present in the list
    function countNodes() {
        $counter = 0;
        //Node current will point to head
        $current = $this->head;
        
        while($current != NULL) {
            //Increment the counter by 1 for each node
            $counter++;
            $current = $current->next;
        }
        return $counter;
    }
    
    //display() will print out the nodes of the list
    function display() {
        //Node current will point to head
        $current = $this->head;
        if($this->head == NULL) {
            print("List is empty <br>");
            return;
        }
        print("Nodes of doubly linked list: <br>");
        while($current != NULL) {
            //Prints each node by incrementing pointer.
            print($current->data . " ");
            $current = $current->next;
        }
    }
}
    
$dList = new CountList();
//Add nodes to the list
$dList->addNode(1);
$dList->addNode(2);
$dList->addNode(3);
$dList->addNode(4);
$dList->addNode(5);
 
//Displays the nodes present in the list
$dList->display();
 
//Counts the nodes present in the given list
print("<br>Count of nodes present in the list: " . $dList->countNodes());
?>
</body>
</html>

输出

Nodes of doubly linked list: 
1 2 3 4 5 
Count of nodes present in the list: 5

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问：创建 N 个节点的双向链表并计算节点数的程序。

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问：创建 N 个节点的双向链表并计算节点数的程序。

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