C++ Linked List Exercises: Count number of nodes in a doubly linked list

Last update on December 20 2024 12:30:10 (UTC/GMT +8 hours)

Write a program in C++ to create a doubly linked list of n nodes and count the number of nodes.

Test Data:
Doubly linked list is as follows:
Traversal in Forward direction:
Orange White Green Red
Traversal in Reverse direction:
Red Green White Orange
Total number of nodes = 4

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
void append_data(Node** head, string new_data)
{
   // 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->next = (*head);
   newNode->prev = NULL;

   // Previous head is the new node
   if ((*head) != NULL)
   (*head)->prev = newNode;

   // Head points to new node
   (*head) = newNode;
}

// Function to count the number of nodes in the doubly linked list
int NodeCount(struct Node* head)
{
  int ctr = 0; // Counter to count the nodes
  while (head != NULL) { // Loop through the linked list until the end is reached
    ctr++; // Increment the counter for each node encountered
    head = head->next; // Move to the next node
  }
  return ctr; // Return the total count of nodes
}

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

// Main program
int main() {
   /* Start with the empty list */
   struct Node* head = NULL; // Initializing the head of the linked list as NULL
   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: ";
   displayDlList(head); // Displaying the doubly linked list
   int totalNode = NodeCount(head); // Calculating the total number of nodes in the list
   cout << "\n\nTotal number of nodes = " << totalNode; // Displaying the total number of nodes
   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

Total number of nodes = 4

Flowchart:

CPP Code Editor:

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Previous C++ Exercise: Reverse doubly linked list.
Next C++ Exercise: Insert a node at the beginning of a Doubly Linked List.