C++ Program to create and display doubly linked list (DLL)

 

Introduction

From this article we are going to implement  doubly linked list using C++ programming language.
In this article we are going to Create and Display the doubly linked list.

Create Doubly Linked list 
To create doubly linked list , the steps are as follows : 

Graphical representation of DLL:


Step 1: Declare a structure named node. In this structure declare one integer data and two pointers : next and prev.

struct node {
       int data;
       node *next;
       node *prev;
};

  
Step 2 : Declare a pointer that stores the address of first node of linked list. Name it as head .  
Initialize it as head = NULL;

Step 3: Create a new node by using new keyword as follows :


node *newNode = new node;

 newNode->data = 10;

 newNode->next = NULL;

 newNode->prev = NULL;

 Step 4: If head ==NULL , assign address of newNode to head .
head = newNode;

Step 5 : Else if head is not NULL , then traverse the linked list till end. Link the next pointer of  last node to the newNode and prev pointer of newNode to the last node of list.
node *temp = head;

while( temp->next !=NULL )
  {
        temp = temp->next;
   }

temp ->next = newnode;

newNode ->prev = temp;

Step 6: By repeating steps through 3 to 5 , you can add as much node as you can. 

 Display the Doubly Linked List 

Steps to display the dll in forward direction .
Step 1 : Create a copy of head pointer , temp and initialize it as  temp = head.

Step 2 : Till reach to the end of linked list , make temp = temp->next and print the output.
 
node *temp = head;
while ( temp !=NULL ) 
{
   cout << temp ->data ;

   temp = temp ->next;
}

 

C++ program to Create and Display the linked list


Download the Code here
#include<iostream>

using namespace std;


struct node
{
    int data;
    node *next;
    node *prev;

};
node *head = NULL;

void create( int val);
void display();

int main()
{
    int choise,input,n;

    do
   {
          cout<<"\n\t\t________________Menu_____________________\n\n";
          cout<<"\t\t  1.Create Doubly Linked List \n";
          cout<<"\t\t  2.Display Doubly Linked List\n";
          cout<<"\t\t  3.Exit \n";
          cout<<" Your Choise : ";
          cin>>choise;

        switch(choise)
        {
          case 1:
            {
                cout<<"How many nodes do you want to insert ? ";
                cin>>n;

                for (int i = 0; i < n; i++)
                {
                    cout<<"Enter the data : ";
                    cin>>input;

                    create(input);  
                }
            }
            break;
          
       case 2:
                {
                    cout<<"Displaying the Doubly Linked List \n";

                    display();
              }
           
          break;
        }

    }while(choise<3);
}

void create(int val)
{
       node *newNode = new node;

       newNode->data = val;

       newNode->next = NULL;

       newNode->prev = NULL;


         if (head ==NULL)
      {
             head = newNode;
      }
     else 
      {
           node *temp = head;

           while(temp->next!=NULL)

           temp = temp->next;

           temp ->next = newNode;

           newNode->prev = temp;
     }
}

void display()
{
    node *temp = head;
    
    while(temp!=NULL)    
    {
          cout<<"\t"<<temp->data<<endl;

          temp = temp->next;
    }

}

Note :  This code is successfully compiled and run under Linux distribution Ubuntu 18.04 LTS environment .  

Output :


    ________________Menu_____________________

        1.Create Doubly Linked List
        2.Display Doubly Linked List
        3.Exit
Your Choise : 1
How many nodes do you want to insert ? 4
Enter the data : 10
Enter the data : 20
Enter the data : 30
Enter the data : 40

        ________________Menu_____________________

        1.Create Doubly Linked List
        2.Display Doubly Linked List
        3.Exit
Your Choise : 2
Displaying the Doubly Linked List
    10
    20
    30
    40

        ________________Menu_____________________

        1.Create Doubly Linked List
        2.Display Doubly Linked List
        3.Exit
Your Choise : 3

Conclusion 

Doubly Linked List is successfully  created and displayed using C++.