﻿ C++ - Insert a node at the beginning of a Doubly Linked List

# C++ Linked List Exercises: Insert a node at the beginning of a Doubly Linked List

## C++ Linked List: Exercise-18 with Solution

Write a C++ program to insert a new node at the beginning of a Doubly Linked List.

Test Data:
Doubly linked list is as follows:
------------------------------
Traversal in Forward direction: Orange White Green Red
Traversal in Reverse direction: Red Green White Orange
Insert a new node at the beginning of a Doubly Linked List:
-------------------------------------------------------------
Traversal in Forward direction: Pink Orange White Green Red
Traversal in Reverse direction: Red Green White Orange Pink

Sample Solution:

C++ Code:

``````#include <iostream> // Including input-output stream header file

using namespace std; // Using standard namespace

// A doubly linked list node
struct Node {
string data; // Data field to store string data
struct Node* next; // Pointer to the next node
struct Node* prev; // Pointer to the previous node
};

// Function to append data at the front of the doubly linked list
{
// Create a new node and allocate memory.
struct Node* newNode = new Node;

// Assign data to the new node
newNode->data = new_data;

// A new node has been added with the name head and the previous node
// set to null, since it is being added at the front.
newNode->prev = NULL;

// Previous head is the new node

// Head points to new node
}

// Function to insert a new node at the beginning of the doubly linked list
{
struct Node* newnode;
{
cout<<"Empty List...!\n"; // Display message if the list is empty
}
else {
struct Node* newNode = new Node;
newNode->data = text;
newNode->prev = NULL;
}
}

// Function to display contents of the doubly linked list
{
Node* last_node;
cout << "\nTraversal in Forward direction: ";
cout << " " << head->data << " "; // Displaying data in forward direction
}
cout << "\nTraversal in Reverse direction: ";
while (last_node != NULL) {
cout << " " << last_node->data << " "; // Displaying data in reverse direction
last_node = last_node->prev;
}
}

// Main program
int main() {
append_data(&head, "Red"); // Appending "Red" at the front of the list
append_data(&head, "Green"); // Appending "Green" at the front of the list
append_data(&head, "White"); // Appending "White" at the front of the list
append_data(&head, "Orange"); // Appending "Orange" at the front of the list
cout<<"Doubly linked list is as follows: ";
cout<<"\n------------------------------";
cout<<"\n\nInsert a new node at the beginning of a Doubly Linked List:";
cout<<"\n-------------------------------------------------------------";
NodeInsertatBegin(&head, "Pink"); // Inserting "Pink" node at the beginning of the list
return 0; // Returning from the main function
}
``````

Sample Output:

```Doubly linked list is as follows:
------------------------------
Traversal in Forward direction:  Orange  White  Green  Red
Traversal in Reverse direction:  Red  Green  White  Orange

Insert a new node at the beginning of a Doubly Linked List:
-------------------------------------------------------------
Traversal in Forward direction:  Pink  Orange  White  Green  Red
Traversal in Reverse direction:  Red  Green  White  Orange  Pink
```

Flowchart:

CPP Code Editor: