问. 在循环链表的中间插入新节点的程序。

2025年3月17日 | 阅读 10 分钟

说明

在此程序中，我们创建一个循环链表，并在列表的中间插入一个新节点。如果列表为空，head 和 tail 都将指向新节点。如果列表不为空，我们将计算列表的大小并除以 2，以获取需要插入新节点的中间点。

Program to insert a new node at the middle of the circular linked list

在列表的中间插入新节点后。

考虑上图，新节点需要添加到列表的中间。首先，我们计算大小，在本例中为 4。因此，为了获得中间点，我们将其除以 2 并将其存储在变量 count 中。我们将定义两个节点 current 和 temp，使得 temp 指向 head，current 指向 temp 前面的节点。我们遍历列表直到到达中间点，方法是将 temp 移动到 temp.next，然后，在新节点 current 和 temp 之间插入新节点。Current 的下一个节点将是 new，new 的下一个节点将是 temp。

算法

定义一个 Node 类，它表示列表中的一个节点。它有两个属性 data 和 next，next 将指向下一个节点。
定义另一个类来创建循环链表，它有两个节点：head 和 tail。变量 size 存储列表的大小。它有两个方法：addInMid() 和 display()。
addInMid() 将节点添加到列表的中间
1. 它首先检查 head 是否为 null（空列表），然后它将节点插入为 head。
2. head 和 tail 都将指向新添加的节点。
3. 如果列表不为空，那么我们计算大小并将其除以 2 以获得中点。
4. 定义节点 temp，它将指向 head，current 将指向 temp 前面的节点。
5. 通过将 temp 递增到 temp.next 来迭代列表，直到到达列表的中间。
6. 新节点将插入在 current 之后和 temp 之前，使得 current 指向新节点，新节点指向 temp。
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 再次指向 head。
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

#Represents the node of list.
class Node:
  def __init__(self,data):
    self.data = data;
    self.next = None;
 
class CreateList:
    #Declaring head and tail pointer as null.
    def __init__(self):
      self.head = Node(None);
      self.tail = Node(None);
      self.head.next = self.tail;
      self.tail.next = self.head;
      self.size = 0;
    
    #This function will add the new node to the list.
    def add(self,data):
       newNode = Node(data);
       #Checks if the list is empty.
       if self.head.data is None:
         #If list is empty, both head and tail would point to new node.
         self.head = newNode;
         self.tail = newNode;
         newNode.next = self.head;
       else:
         #tail will point to new node.
         self.tail.next = newNode;
         #New node will become new tail.
         self.tail = newNode;
         #Since, it is circular linked list tail will points to head.
         self.tail.next = self.head;
       #Size will count the number of element in the list
       self.size = self.size+1;
    
    #This function will add the new node at the middle of the list.
    def addInMid(self,data):
        newNode = Node(data);
        #Checks if the list is empty.
        if(self.head == None):
            #If list is empty, both head and tail would point to new node.
            self.head = newNode;
            self.tail = newNode;
            newNode.next = self.head;
        else:
            #Store the mid-point of the list
            count = (self.size//2) if (self.size % 2 == 0) else ((self.size+1)//2);
            #temp will point to head
            temp = self.head;
            for i in range(0,count):
                #Current will point to node previous to temp.
                current = temp;
                #Traverse through the list till the middle of the list is reached
                temp = temp.next;
            #current will point to new node
            current.next = newNode;
            #new node will point to temp
            newNode.next = temp;
        self.size = self.size+1;
        
    #Displays all the nodes in the list
    def display(self):
      current = self.head;
      if self.head is None:
        print("List is empty");
        return;
      else:
          #Prints each node by incrementing pointer.
          print(current.data),
          while(current.next != self.head):
              current = current.next;
              print(current.data),
    
 
class CircularLinkedList:
    cl = CreateList();
    #Adds data to the list
    cl.add(1);
    cl.add(2);
    cl.add(3);
    cl.add(4);
    print("Original list: ");
    cl.display();
    #Inserting node '5' in the middle
    cl.addInMid(5);
    print("\nUpdated List: ");
    cl.display();
    #Inserting node '6' in the middle
    cl.addInMid(6);
    print("\nUpdated List: ");
    cl.display();

输出

Original list: 
1 2 3 4
Updated List: 
1 2 5 3 4
Updated List: 
1 2 5 6 3 4

C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
 
//Represents the node of list.
struct node{
    int data;
    struct node *next;
};
 
//Declaring head and tail pointer as null.
struct node *head = NULL;
struct node *tail = NULL;
int size = 0;
 
//This function will add the new node to the list.
void add(int data){
    //Create new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    //Checks if the list is empty.
    if(head == NULL){
        //If list is empty, both head and tail would point to new node.
        head = newNode;
        tail = newNode;
        newNode->next = head;
    }else {
        //tail will point to new node.
        tail->next = newNode;
        //New node will become new tail.
        tail = newNode;
        //Since, it is circular linked list tail will point to head.
        tail->next = head;
    }
  size++;
}
 
//This function will add the new node at the middle of the list.
void addInMid(int data){
    int i;
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    //Checks if the list is empty.
    if(head == NULL){
        //If list is empty, both head and tail would point to new node.
        head = newNode;
        tail = newNode;
        newNode->next = head;
    }
    else{
           struct node *temp, *current = NULL;
        //Store the mid-point of the list
        int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);    
        //temp will point to head
        temp = head;
        for(i = 0; i < count; i++){
            //Current will point to node previous to temp.
            current = temp;
            //Traverse through the list till the middle of the list is reached
            temp = temp->next;
        }
        //current will point to new node
        current->next = newNode;
        //new node will point to temp
        newNode->next = temp;
   }
    size++;
}
 
//This function will display the nodes of circular linked list
void display(){
    struct node *current = head;
    if(head == NULL){
        printf("List is empty");
    }
    else{
         do{
          //Prints each node by incrementing pointer.
            printf("%d ", current->data);
            current = current->next;
        }while(current != head);
        printf("\n");
    }
}
    
int main()
{
  //Adds data to the list
    add(1);
    add(2);
    add(3);
    add(4);
    
    printf("Original list:\n ");
    display();
    
    //Inserting node '5' in the middle
    addInMid(5);
    printf("Updated List:\n ");
    display();
    
    //Inserting node '6' in the middle
    addInMid(6);
    printf("Updated List:\n ");
    display();
   
   return 0;
}

输出

Original list: 
1 2 3 4
Updated List: 
1 2 5 3 4
Updated List: 
1 2 5 6 3 4

JAVA

public class InsertInMid {
    //Represents the node of list.
        public class Node{
            int data;
            Node next;
            public Node(int data) {
                this.data = data;
            }
        }
        
        public int size;
        //Declaring head and tail pointer as null.
        public Node head = null;
        public Node tail = null;
        
        //This function will add the new node to the list.
        public void add(int data){
            //Create new node
            Node newNode = new Node(data);
            //Checks if the list is empty.
            if(head == null) {
                 //If list is empty, both head and tail would point to new node.
                head = newNode;
                tail = newNode;
                newNode.next = head;
            }
            else {
                //tail will point to new node.
                tail.next = newNode;
                //New node will become new tail.
                tail = newNode;
                //Since, it is circular linked list tail will points to head.
                tail.next = head;
            }
            //Size will count the number of element in the list
            size++;
        }
        
        //This function will add the new node at the middle of the list.
        public void addInMid(int data){
            Node newNode = new Node(data);
            //Checks if the list is empty.
            if(head == null){
                //If list is empty, both head and tail would point to new node.
                head = newNode;
                tail = newNode;
                newNode.next = head;
            }
            else{
                Node temp,current;
                //Store the mid-point of the list
                int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);    
                //temp will point to head
                temp = head;
                current= null;
                for(int i = 0; i < count; i++){
                    //Current will point to node previous to temp.
                    current = temp;
                    //Traverse through the list till the middle of the list is reached
                    temp = temp.next;
                }
 
                //current will point to new node
                current.next = newNode;
                //new node will point to temp
                newNode.next = temp;
            }
            size++;
        }
        
        //Displays all the nodes in the list
        public void display() {
            Node current = head;
            if(head == null) {
                System.out.println("List is empty");
            }
            else {
                 do{
                    //Prints each node by incrementing pointer.
                    System.out.print(" "+ current.data);
                    current = current.next;
                }while(current != head);
                System.out.println();
            }
        }
        
        public static void main(String[] args) {
            InsertInMid cl = new InsertInMid();
            //Adds data to the list
            cl.add(1);
            cl.add(2);
            cl.add(3);
            cl.add(4);
            
            System.out.println("Original list: ");
            cl.display();
            
            //Inserting node '5' in the middle
            cl.addInMid(5);
            System.out.println( "Updated List: ");
            cl.display();
            
            //Inserting node '6' in the middle
            cl.addInMid(6);
            System.out.println("Updated List: ");
            cl.display();
        }
}

输出

Original list: 
1 2 3 4
Updated List: 
1 2 5 3 4
Updated List: 
1 2 5 6 3 4

C#

using System; 
namespace CircularLinkedList 
{                     
    public class Program
    {
        //Represents the node of list.
        public class Node<T>{
            public T data;
            public Node<T> next;
            public Node(T value) {
                data = value;
                next = null;
            }
        }
        
        public class CreateList<T>{
            protected Node<T> head = null;             
             protected Node<T> tail = null;
            int size = 0;
            
            //This function will add the new node to the list.
            public void add(T data){
                //Create new node
                Node<T> newNode = new Node<T>(data);
                //Checks if the list is empty.
                if(head == null){
                    head = newNode;
                    tail = newNode;
                    newNode.next = head;
                }else{
                    //tail will point to new node.
                    tail.next = newNode;
                    //New node will become new tail.
                    tail = newNode;
                    //Since, it is circular linked list tail will points to head.
                    tail.next = head;
                }
                size++;
            }
            
            //This function will add the new node at the middle of the list.
            public void addInMid(T data){
                Node<T> newNode = new Node<T>(data);
                //Checks if the list is empty.
                if(head == null){
                    //If list is empty, both head and tail would point to new node.
                    head = newNode;
                    tail = newNode;
                    newNode.next = head;
                }
                else{
                    Node<T> temp,current;
                    //Store the mid-point of the list
                    int count = (size % 2 == 0) ? (size/2) : ((size+1)/2);    
                    //temp will point to head
                    temp = head;
                    current= null;
                    for(int i = 0; i < count; i++){
                        //Current will point to node previous to temp.
                        current = temp;
                        //Traverse through the list till the middle of the list is reached
                        temp = temp.next;
                    }
    
                    //current will point to new node
                    current.next = newNode;
                    //new node will point to temp
                    newNode.next = temp;
                }
                size++;
               }
            
            //Displays all the nodes in the list
            public void display(){
                Node<T> current = head;
                if(head == null){
                    Console.WriteLine("List is empty");
                }
                else{
                    do{
                        //Prints each node by incrementing pointer.
                        Console.Write(" "+ current.data);
                        current = current.next;
                    }while(current != head);
                }    
            }
        }
        
        public static void Main()
        {
            
        CreateList<int> cl = new CreateList<int>();
            //Adds data to the list
            cl.add(1);
            cl.add(2);
            cl.add(3);
            cl.add(4);
            
            Console.WriteLine("Original list: ");
            cl.display();
            
            //Inserting node '5' in the middle
            cl.addInMid(5);
            Console.WriteLine();
            Console.WriteLine("Updated List: ");
            cl.display();
            
            //Inserting node '6' in the middle
            cl.addInMid(6);
            Console.WriteLine();
            Console.WriteLine("Updated List: ");
            cl.display();
        }
    }
}

输出

Original list: 
1 2 3 4
Updated List: 
1 2 5 3 4
Updated List: 
1 2 5 6 3 4

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represents the node of list.
class Node{
    public $data;
    public $next;
    function __construct($data){
        $this->data = $data;
        $this->next = NULL;
    }
}
class CreateList{
    //Declaring head and tail pointer as null.
    private $head;
    private $tail;
    private $size;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
        $this->size = 0;
    }
    
    //This function will add the new node to the list.
    function add($data){
        //Create new node
        $newNode = new Node($data);
        //Checks if the list is empty.
        if($this->head == NULL){
            //If list is empty, both head and tail would point to new node.
            $this->head = $newNode;
            $this->tail = $newNode;
            $newNode->next = $this->head;
        }
        else{
            //tail will point to new node.
            $this->tail->next = $newNode;
            //New node will become new tail.
            $this->tail = $newNode;
            //Since, it is circular linked list tail will point to head.
            $this->tail->next = $this->head;
        }
        $this->size++;
    }
    
    //This function will add the new node at the middle of the list.
    function addInMid($data){
        $newNode = new Node($data);
        //Checks if the list is empty.
        if($this->head == NULL){
            //If list is empty, both head and tail would point to new node.
            $this->head = $newNode;
            $this->tail = $newNode;
            $newNode->next = $this->head;
        }
        else{
            //Store the mid-point of the list
            $count = ($this->size % 2 == 0) ? ($this->size/2):(($this->size+1)/2);    
            //temp will point to head
            $temp = $this->head;
            for($i = 0; $i < $count; $i++){
                //Current will point to node previous to temp.
                $current = $temp;
                //Traverse through the list till the middle of the list is reached
                $temp = $temp->next;
            }
 
            //$current will point to new node
            $current->next = $newNode;
            //new node will point to temp
            $newNode->next = $temp;
        }
        $this->size++;
    }
    
    //Displays all the nodes in the list
    function display() {
        $current = $this->head;
        if($this->head == NULL) {
            echo "List is empty";
        }
        else {
             do{
                echo(" $current->data");
                $current = $current->next;
            }while($current != $this->head);
            echo "<br>";
        }
    }   
}
$cl = new CreateList();
//Adds data to the list
$cl->add(1);
$cl->add(2);
$cl->add(3);
$cl->add(4);
echo "Original list: <br>";
$cl->display();
//Inserting node '5' in the middle
$cl->addInMid(5);
echo "Updated List: <br>";
$cl->display();
//Inserting node '6' in the middle
$cl->addInMid(6);
echo "Updated List: <br>";
$cl->display();
?>
</body>
</html>

输出

Original list: 
1 2 3 4
Updated List: 
1 2 5 3 4
Updated List: 
1 2 5 6 3 4

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问. 在循环链表的中间插入新节点的程序。

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问. 在循环链表的中间插入新节点的程序。

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