C program to count nodes in Circular Linked List

Quick links

Write a C program to count nodes in Circular Linked List. In this example I will explain how to count nodes in Circular Linked List. C program to create a Circular Linked List and count total elements in Circular Linked List.

Count nodes in Circular Linked List

Required knowledge

Do while loop, Functions, Pointers, Structures, Dynamic Memory Allocation

Logic to count nodes in a Circular Linked List

Step by step descriptive logic to count nodes in a circular linked list.

  1. Create a Circular Linked List and assign reference of first node to head.
  2. Initialize count = 0; variable to store total nodes in list.
  3. Initialize another variable to traverse list, say current = head;.
  4. Increment count++ and current = current->next;.
  5. Repeat step 4 till you reach head node after traversing once.

Program to count nodes in Circular Linked List

/**
 * C program to count nodes in a Circular Linked List
 */

#include <stdio.h>
#include <stdlib.h>


/* Basic structure of node */
struct node {
    int data;
    struct node * next;
};


/* Function declaration */
void createList(struct node **head, int n);
void displayList(struct node *head);
int  count(struct node *head);


int main()
{
    int n, choice;

    struct node *head = NULL;

    /*
     * Run forever until user chooses 0
     */
    while(choice != 0)
    {
        printf("--------------------------------------------\n");
        printf("        CIRCULAR LINKED LIST PROGRAM        \n");
        printf("--------------------------------------------\n");
        printf("1. Create List\n");
        printf("2. Display list\n");
        printf("3. Count nodes\n");
        printf("0. Exit\n");
        printf("--------------------------------------------\n");
        
        printf("Enter your choice : ");
        scanf("%d", &choice);

        switch(choice)
        {
            case 1:
                printf("Enter total node to create: ");
                scanf("%d", &n);
                createList(&head, n);
                break;
            
            case 2:
                displayList(head);
                getchar(); // Hold screen
                getchar(); // Hold screen
                break;
            
            case 3:
                printf("Total nodes = %d\n", count(head));
                getchar(); // Hold screen
                getchar(); // Hold screen
                break;

            case 0:
                printf("Exiting from application");
                exit(0);
                break;

            default:
                printf("Error! Invalid choice. Please choose between 0-3");
        }

        printf("\n\n\n\n\n");
    }

    return 0;
}


/**
 * Function to count total number of nodes in Circular Linked List
 */
int count(struct node *head)
{
    int total = 0;
    struct node *current = head;

    // Iterate till end of list
    do 
    {
        current = current->next;
        total++;
    } while (current != head);

    // Return total nodes in list
    return total;
}


/**
 * Creates a circular linked list of n nodes.
 */
void createList(struct node **head, int n)
{
    int i, data;
    struct node *prevNode, *newNode;

    prevNode = NULL;
    newNode  = NULL;


    /* Creates and links rest of the n-1 nodes */
    for(i=1; i<=n; i++)
    {
        // Create a new node
        newNode = (struct node *) malloc(sizeof(struct node));

        printf("Enter data of %d node: ", i);
        scanf("%d", &data);

        newNode->data = data;
        newNode->next = NULL;

        // Link the previous node with newly created node
        if (prevNode != NULL)
            prevNode->next = newNode;

        // Move the previous node ahead
        prevNode = newNode;

        // Link head node if not linked
        if (*head == NULL)
            *head = newNode;
    }

    // Link last node with first node
    prevNode->next = *head;

    printf("\nCIRCULAR LINKED LIST CREATED SUCCESSFULLY\n");
}


/**
 * Display node content of circular linked list
 */
void displayList(struct node *head)
{
    struct node *current;
    int n = 1;

    // Nothing to print in list
    if(head == NULL)
    {
        printf("List is empty.\n");
        return;
    }


    current = head;
    printf("DATA IN THE LIST:\n");

    do 
    {
        // Print current node
        printf("Data %d = %d\n", n++, current->data);

        // Move to next node
        current = current->next;
    } while (current != head);
}

Output

--------------------------------------------
        CIRCULAR LINKED LIST PROGRAM
--------------------------------------------
1. Create List
2. Display list
3. Count nodes
0. Exit
--------------------------------------------
Enter your choice : 1
Enter total node to create: 5
Enter data of 1 node: 10
Enter data of 2 node: 20
Enter data of 3 node: 30
Enter data of 4 node: 40
Enter data of 5 node: 50

CIRCULAR LINKED LIST CREATED SUCCESSFULLY





--------------------------------------------
        CIRCULAR LINKED LIST PROGRAM
--------------------------------------------
1. Create List
2. Display list
3. Count nodes
0. Exit
--------------------------------------------
Enter your choice : 2
DATA IN THE LIST:
Data 1 = 10
Data 2 = 20
Data 3 = 30
Data 4 = 40
Data 5 = 50






--------------------------------------------
        CIRCULAR LINKED LIST PROGRAM
--------------------------------------------
1. Create List
2. Display list
3. Count nodes
0. Exit
--------------------------------------------
Enter your choice : 3
Total nodes = 5






--------------------------------------------
        CIRCULAR LINKED LIST PROGRAM
--------------------------------------------
1. Create List
2. Display list
3. Count nodes
0. Exit
--------------------------------------------
Enter your choice : 0
Exiting from application

Happy coding 😉

About Pankaj

Pankaj Prakash is the founder, editor and blogger at Codeforwin. He loves to learn new techs and write programming articles especially for beginners. He works at Vasudhaika Software Sols as a Software Design Engineer and manages Codeforwin. In short Pankaj is Web developer, Blogger, Learner, Tech and Music lover.

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