C Exercises: Delete node from the beginning of a circular linked list

Last update on December 20 2024 13:18:33 (UTC/GMT +8 hours)

Write a program in C to delete a node from the beginning of a circular linked list.

Visual Presentation:

C Exercises: Delete node from the beginning of a circular linked list

Sample Solution:

C Code:

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


// Structure definition for a node in a circular linked list
struct node {
    int num;
    struct node *nextptr;
} *stnode;

// Function prototypes
void ClListcreation(int n);
void ClListDeleteFirstNode();
void displayClList(int a);

int main() {
    int n, a;
    stnode = NULL; // Initializing the start pointer of the circular list to NULL

    // User input for the number of nodes
    printf("\n\n Circular Linked List : Delete node from the beginning of a circular linked list :\n");
    printf("--------------------------------------------------------------------------------------\n");
    printf(" Input the number of nodes : ");
    scanf("%d", &n);

    // Creating a circular linked list
    ClListcreation(n);
    a = 1; // Flag to display the initial list
    displayClList(a);

    // Deleting the first node from the circular list
    ClListDeleteFirstNode();
    a = 2; // Flag to display the list after deletion
    displayClList(a);

    return 0;
}

// Function to create a circular linked list
void ClListcreation(int n) {
    int i, num;
    struct node *preptr, *newnode;

    if (n >= 1) {
        // Allocating memory for the first node and initializing it
        stnode = (struct node *)malloc(sizeof(struct node));
        printf(" Input data for node 1 : ");
        scanf("%d", &num);
        stnode->num = num;
        stnode->nextptr = NULL;
        preptr = stnode;

        // Loop to create subsequent nodes and link them to form a circular list
        for (i = 2; i <= n; i++) {
            newnode = (struct node *)malloc(sizeof(struct node));
            printf(" Input data for node %d : ", i);
            scanf("%d", &num);
            newnode->num = num;
            newnode->nextptr = NULL;
            preptr->nextptr = newnode;
            preptr = newnode;
        }
        preptr->nextptr = stnode; // Linking the last node with the first node to form a circular list
    }
}

// Function to delete the first node from the circular linked list
void ClListDeleteFirstNode() {
    struct node *p = stnode;
    struct node *store;

    while (p->nextptr != stnode) {
        p = p->nextptr;
    }
    store = stnode;
    stnode = stnode->nextptr;
    printf("\n The deleted node is -> %d", store->num);
    p->nextptr = stnode;
    free(store);
}

// Function to display the circular linked list
void displayClList(int m) {
    struct node *tmp;
    int n = 1;

    if (stnode == NULL) {
        printf(" No data found in the List yet.");
    } else {
        tmp = stnode;
        if (m == 1) {
            printf("\n Data entered in the list are :\n");
        } else {
            printf("\n After deletion the new list are :\n");
        }

        // Loop to display nodes in the circular list
        do {
            printf(" Data %d = %d\n", n, tmp->num);
            tmp = tmp->nextptr;
            n++;
        } while (tmp != stnode);
    }
}

Sample Output:

 Circular Linked List : Delete node from the beginning of a circular linked list :                            
--------------------------------------------------------------------------------------                        
 Input the number of nodes : 3                                                                                
 Input data for node 1 : 2                                                                                    
 Input data for node 2 : 5                                                                                    
 Input data for node 3 : 8                                                                                    
                                                                                                              
 Data entered in the list are :                                                                               
 Data 1 = 2                                                                                                   
 Data 2 = 5                                                                                                   
 Data 3 = 8                                                                                                   
                                                                                                              
 The deleted node is -> 2                                                                                     
 After deletion the new list are :                                                                            
 Data 1 = 5                                                                                                   
 Data 2 = 8

Flowchart: