Description

To delete a node in the beginning of circular linked list -
Case 1: Check if list is empty
	Show message that list is empty.
Case 2: If List has one element
	Assign NULL to haed.
Case 2: If list has elements
	a) Traverse the list until last node contain the address of first node
	b) Assign the next field of head to next field of last node
	c) Assign the last node next field to head.
	
Note: Here head contains the address of first node

C/C++

#include<stdio.h>
#include<malloc.h>

struct node *createCircularLinkedList(int);
void displayCircularLinkedList(struct node *);
struct node *delete_beg(struct node *);

//Declaring node
struct node{
    int data;
    struct node *next;
};

int main(){
    int n;
    struct node *head;

    printf("Enter the size of linked list : ");
    scanf("%d",&n);

    //Calling function to create node
    head=createCircularLinkedList(n);

    //Calling function to display list
    displayCircularLinkedList(head);

    //Code to delete a node from beginning
    head=delete_beg(head);
    printf("\nThe linked list after deletion of node from beginning - \n");

    //Calling function to display list after deletion of node from beginning
    displayCircularLinkedList(head);

    return 0;
}

struct node *createCircularLinkedList(int n){
    int i;
    struct node *head=NULL;
    struct node *newNode, *ptr;

    for(i=0;i<n;i++){
        //Creating a node
        newNode=(struct node *)malloc(sizeof(struct node));

        //Assigning data to newly created node
        printf("Enter %d node data : ",(i+1));
        scanf("%d",&newNode->data);

        /*If list is empty assign the address of newly created node
        to head*/
        if(head==NULL){
            newNode->next=newNode;
            head=newNode;
        }else{
            /* If list already have few elements then loop through
            list and add newly created node at the end of list*/
            ptr=head;
            while(ptr->next!=head){
                ptr=ptr->next;
            }
            ptr->next=newNode;
            newNode->next=head;
        }
    }
    return head;
}

void displayCircularLinkedList(struct node *head){
    struct node *ptr;

    //If list is empty
    if(head==NULL){
        printf("The Linked List is Empty");
    }else{
        /*If list has elements then loop through the loop and
        print elements one by one in sequential manner*/
        ptr=head;
        while(ptr->next!=head){
            printf("The value of node is %d and their address is %u\n",ptr->data,ptr);
            ptr=ptr->next;
        }
        printf("The value of node is %d and their address is %u\n",ptr->data,ptr);
    }
}

//Function to delete a node from beginning
struct node *delete_beg(struct node *head){

    //No node is available to delete
    if(head==NULL){
        printf("\nLink list is empty...No node to delete!!");
    }else if(head->next==head){
        head=NULL;
        free(head);
    }else{

        struct node *ptr;
        ptr=head;

        while(ptr->next!=head){
            ptr=ptr->next;
        }
        ptr->next=head->next;
        free(head);
        head=ptr->next;
    }
    return head;
}

Java

import java.io.*;
import java.util.Scanner;

public class DeleteNodeBeginningCircularSinglyLinkedList {

    //Declaring node
    class Node{
        int data;
        Node next;
        public Node(int data) {
            this.data=data;
            
            //Assigning null value to the next field
            this.next=null;
        }
    }
    
    public Node head=null;
    
    //Function to add node
    public void addNode(int data) {
        
        //Creating a new node
        Node newNode = new Node(data);
        
        /*If list is empty assign the address of newly created node
        to head*/
        if(head==null) {
            newNode.next=newNode;
            head=newNode;
        }else {
            
            /* If list already have few elements then loop through 
            list and add newly created node at the end of list*/
            Node tail=head;
            while(tail.next!=head) {
                tail=tail.next;
            }
            tail.next=newNode;
            newNode.next=head;
        }
    }
    
    public void display() {
        Node ptr=head;
        
        //If list is empty
        if(ptr==null) {
            System.out.println("The list is empty");
            return;
        }
        System.out.println("The nodes of lists are : ");
        
       /*If list has elements then loop through the loop and 
       print elements one by one in sequential manner*/
        while(ptr.next!=head) {
            System.out.print(ptr.data+" ");
            ptr=ptr.next;
        }
        System.out.print(ptr.data+" ");
    }

    public static void main(String[] args) {
        
        Scanner scanner = new Scanner(System.in);
        
        DeleteNodeBeginningCircularSinglyLinkedList list =
                                  new DeleteNodeBeginningCircularSinglyLinkedList();
        
        System.out.println("Enter number of nodes : ");
        int n = scanner.nextInt();
        
        for(int i=0;i<n;i++) {
            System.out.println("Enter value of "+(i+1)+" node : ");
            int val = scanner.nextInt();
            list.addNode(val);
        }
        
        //Calling function to display list
        list.display();
        
        list.delete_beg();
        
        // Calling function to display list after deletion of node from beginning
        System.out.println("\nAfter deletion of node from beginning - ");
        list.display();
    }

    private void delete_beg() {
        //No node is available to delete
        if(head==null){
            System.out.println("Link list is empty...No node to delete!!");
        }else if(head.next==head){
            head=null;
        }else{

            Node ptr=head;

            while(ptr.next!=head){
                ptr=ptr.next;
            }
            ptr.next=head.next;
            head=ptr.next;
        }
    }
}

Related Programs