在单向链表开头插入新节点的程序

2025年3月17日 | 阅读 7 分钟

说明

在此程序中，我们将创建一个单链表，并在列表的开头添加一个新节点。要完成此任务，我们将头部存储到一个临时节点 temp 中。将新添加的节点设为列表的新头部。然后，将 temp（旧头部）添加到新头部之后。

Program to insert a new node at the beginning of the singly linked list

考虑上面的列表；节点 1 代表原始列表的头部。设节点 New 为需要添加到列表开头的节点。节点 temp 将指向头部，即 1。将 New 设为列表的新头部，并将 temp 添加到新头部之后，使得 New 后面的节点为 1。

算法

创建一个名为 Node 的类，它有两个属性：data 和 next。Next 是指向链表中下一个节点的指针。
创建另一个名为 InsertStart 的类，它有两个属性：head 和 tail。
addAtStart() 将在新节点添加到列表的开头
1. 它首先检查 head 是否等于 null，这意味着列表为空。
2. 如果列表为空，则 head 和 tail 都将指向新添加的节点。
3. 如果列表不为空，则创建临时节点 temp 将指向头部。
4. 将新节点添加为列表的头部。
5. temp 原来指向旧头部，将被添加到新头部之后。
display() 将显示列表中存在的节点
1. 定义一个节点 current，它最初将指向列表的 head。
2. 遍历列表直到 current 指向 null。
3. 通过使 current 在每次迭代中指向它的下一个节点来显示每个节点。

解决方案

Python

#Represent a node of the singly linked list
class Node:
    def __init__(self,data):
        self.data = data;
        self.next = None;
        
class InsertStart:
    #Represent the head and tail of the singly linked list
    def __init__(self):
        self.head = None;
        self.tail = None;
        
    #addAtStart() will add a new node to the beginning of the list
    def addAtStart(self, data):
        #Create a new node
        newNode = Node(data);
        
        #Checks if the list is empty
        if(self.head == None):
            #If list is empty, both head and tail will point to new node
            self.head = newNode;
            self.tail = newNode;
        else:
            #Node temp will point to head
            temp = self.head;
            #newNode will become new head of the list
            self.head = newNode;
            #Node temp(previous head) will be added after new head
            self.head.next = temp;
            
    #display() will display all the nodes present in the list
    def display(self):
        #Node current will point to head
        current = self.head;
        
        if(self.head == None):
            print("List is empty");
            return;
            
        print("Adding nodes to the start of the list: ");
        while(current != None):
            #Prints each node by incrementing pointer
            print(current.data ),
            current = current.next;
       
 
sList = InsertStart();
 
#Adding 1 to the list
sList.addAtStart(1);
sList.display();
#Adding 2 to the list
sList.addAtStart(2);
sList.display();
#Adding 3 to the list
sList.addAtStart(3);
sList.display();
#Adding 4 to the list
sList.addAtStart(4);
sList.display();

输出

Adding nodes to the start of the list: 
1 
Adding nodes to the start of the list: 
2 1 
Adding nodes to the start of the list: 
3 2 1 
Adding nodes to the start of the list: 
4 3 2 1

C

#include <stdio.h>
 
//Represent a node of the singly linked list
struct node{
    int data;
    struct node *next;
};    
 
//Represent the head and tail of the singly linked list
struct node *head, *tail = NULL;
 
//addAtStart() will add a new node to the beginning of the list
void addAtStart(int data) {
    //Create a new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    newNode->next = NULL;
    
    //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 {
        //Node temp will point to head
        struct node *temp = head;
        //newNode will become new head of the list
        head = newNode;
        //Node temp(previous head) will be added after new head
        head->next = temp;
    }
}
    
//display() will display all the nodes present in the list
void display() {
    //Node current will point to head
    struct node *current = head;
    
    if(head == NULL) {
        printf("List is empty\n");
        return;
    }
    printf("Adding nodes to the start of the list: \n");
    while(current != NULL) {
        //Prints each node by incrementing pointer
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");
}
    
int main()
{
    //Adding 1 to the list
    addAtStart(1);
    display();
    
    //Adding 2 to the list
    addAtStart(2);
    display();
    
    //Adding 3 to the list
    addAtStart(3);
    display();
    
    //Adding 4 to the list
    addAtStart(4);
    display();
 
    return 0;
}

输出

Adding nodes to the start of the list: 
1 
Adding nodes to the start of the list: 
2 1 
Adding nodes to the start of the list: 
3 2 1 
Adding nodes to the start of the list: 
4 3 2 1

JAVA

public class InsertStart {
    
    //Represent a node of the singly linked list
    class Node{
        int data;
        Node next;
        
        public Node(int data) {
            this.data = data;
            this.next = null;
        }
    }
 
    //Represent the head and tail of the singly linked list
    public Node head = null;
    public Node tail = null;
    
    //addAtStart() will add a new node to the beginning of the list
    public void addAtStart(int data) {
        //Create a new node
        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 {
            //Node temp will point to head
            Node temp = head;
            //newNode will become new head of the list
            head = newNode;
            //Node temp(previous head) will be added after new head
            head.next = temp;
        }
    }
    
    //display() will display all the nodes present in 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("Adding nodes to the start of the list: ");
        while(current != null) {
            //Prints each node by incrementing pointer
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }
    
    public static void main(String[] args) {
        
        InsertStart sList = new InsertStart();
        
        //Adding 1 to the list
        sList.addAtStart(1);
        sList.display();
        
        //Adding 2 to the list
        sList.addAtStart(2);
        sList.display();
        
        //Adding 3 to the list
        sList.addAtStart(3);
        sList.display();
        
        //Adding 4 to the list
        sList.addAtStart(4);
        sList.display();
    }
}

输出

Adding nodes to the start of the list: 
1 
Adding nodes to the start of the list: 
2 1 
Adding nodes to the start of the list: 
3 2 1 
Adding nodes to the start of the list: 
4 3 2 1

C#

using System;
                    
public class CreateList
{
    //Represent a node of the singly linked list
    public class Node<T>{
        public T data;
        public Node<T> next;
        
        public Node(T value) {
            data = value;
            next = null;
        }
    }
        
    public class InsertStart<T>{
        //Represent the head and tail of the singly linked list
        public Node<T> head = null;             
         public Node<T> tail = null;
    
        //addAtStart() will add a new node to the beginning of the list
        public void addAtStart(T data) {
            //Create a new node
            Node<T> newNode = new Node<T>(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 {
                //Node temp will point to head
                Node<T> temp = head;
                //newNode will become new head of the list
                head = newNode;
                //Node temp(previous head) will be added after new head
                head.next = temp;
            }
        }
 
        //display() will display all the nodes present in 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("Adding nodes to the start of the list: ");
            while(current != null) {
                //Prints each node by incrementing pointer
                Console.Write(current.data + " ");
                current = current.next;
            }
            Console.WriteLine();
        }
    }
    
    public static void Main()
    {
        InsertStart<int> sList = new InsertStart<int>();
        
        //Adding 1 to the list
        sList.addAtStart(1);
        sList.display();
        
        //Adding 2 to the list
        sList.addAtStart(2);
        sList.display();
        
        //Adding 3 to the list
        sList.addAtStart(3);
        sList.display();
        
        //Adding 4 to the list
        sList.addAtStart(4);
        sList.display();    
    }
}

输出

Adding nodes to the start of the list: 
1 
Adding nodes to the start of the list: 
2 1 
Adding nodes to the start of the list: 
3 2 1 
Adding nodes to the start of the list: 
4 3 2 1

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represent a node of singly linked list
class Node{
    public $data;
    public $next;
    
    function __construct($data){
        $this->data = $data;
        $this->next = NULL;
    }
}
class InsertStart{
    //Represent the head and tail of the singly linked list
    public $head;
    public $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    
    //addAtStart() will add a new node to the beginning of the list
    function addAtStart($data) {
        //Create a new node
        $newNode = new Node($data);
        
        //Checks if the list is empty
        if($this->head == null) {
            //If list is empty, both head and tail will point to new node
            $this->head = $newNode;
            $this->tail = $newNode;
        }
        else {
            //Node temp will point to head
            $temp = $this->head;
            //newNode will become new head of the list
            $this->head = $newNode;
            //Node temp(previous head) will be added after new head
            $this->head->next = $temp;
        }
    }
    
    //display() will display all the nodes present in the list
    function display() {
        //Node current will point to head
        $current = $this->head;
        
        if($this->head == NULL) {
            print("List is empty <br>");
            return;
        }
        print("Adding nodes to the start of the list: <br>");
        while($current != NULL) {
            //Prints each node by incrementing pointer
            print($current->data . " ");
            $current = $current->next;
        }
        print("<br>");
    }
}
    
$sList = new InsertStart();
        
//Adding 1 to the list
$sList->addAtStart(1);
$sList->display();
 
//Adding 2 to the list
$sList->addAtStart(2);
$sList->display();
 
//Adding 3 to the list
$sList->addAtStart(3);
$sList->display();
 
//Adding 4 to the list
$sList->addAtStart(4);
$sList->display();
?>
</body>
</html>

输出

Adding nodes to the start of the list: 
1 
Adding nodes to the start of the list: 
2 1 
Adding nodes to the start of the list: 
3 2 1 
Adding nodes to the start of the list: 
4 3 2 1

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在单向链表开头插入新节点的程序

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