circular_linklist000001.cpp

#include <iostream>
#include <stdlib.h>
using namespace std;

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

void trivarsal(struct node *head)
{
    struct node *ptr= head;
    do
    {
        cout<<"Elements are :- "<<ptr->data<<endl;
        ptr=ptr->next;
    } while (ptr!=head);
    
}
// circular link list insert at first
struct node *InsetAtFirst(struct node *head,int  data){
    struct node *ptr;
    ptr = (struct node *)malloc(sizeof(struct node));
    ptr->data = data;
    struct node *p = head->next;

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

}
// case 1 --> delete at first
// struct node *Deleteatfirst(struct node *head){
//     struct node *ptr=head;
//     head=head->next;
//     free(ptr);
//     return head;
// }

// case 2 --> deletion a element at given index
// struct node *DeleteAtIndex(struct node *head,int index){
//     struct node *ptr=head;
//     struct node *q = head->next;
//     for(int i=0;i<index-1;i++){
//         ptr->next;
//         q->next;
//     }
//     ptr->next = q->next;
//     free(q);
//     return head;

// case 3 :- delete at last element
// struct node *DeleteAtLast(struct node *head)
// {
//     struct node *p = head;
//     struct node *q = head->next;
//     while (q->next != NULL)
//     {
//         p = p->next;
//         q = p->next;
//     }
//     p->next = NULL;
//     free(q);
//     return head;
// }

int main()
{
    struct node *head;
    struct node *second;
    struct node *third;
    struct node *fourth;
    struct node *fifth;
    struct node *six;
    struct node *seven;
    struct node *eight;
    head = (struct node *)malloc(sizeof(struct node));
    second = (struct node *)malloc(sizeof(struct node));
    third = (struct node *)malloc(sizeof(struct node));
    fourth = (struct node *)malloc(sizeof(struct node));
    fifth = (struct node *)malloc(sizeof(struct node));
    six = (struct node *)malloc(sizeof(struct node));
    seven = (struct node *)malloc(sizeof(struct node));
    eight = (struct node *)malloc(sizeof(struct node));


    head->data = 1;
    head->next = second;

    second->data = 2;
    second->next = third;

    third->data = 3;
    third->next = fourth;

    fourth->data = 4;
    fourth->next = fifth;

    fifth->data = 5;
    fifth->next = six;

    six->data = 6;
    six->next = seven;

    seven->data = 7;
    seven->next = eight;

    eight->data = 8;
    eight->next = head;




    cout << "before insert in circular link list :- " << endl;
    trivarsal(head);
    cout << "After insert in circular link list At first :- " << endl;
    head=InsetAtFirst(head,99);
    trivarsal(head);
    // head = Deleteatfirst(head);
    // cout<<"after deletion :- "<<endl;
    // trivarsal(head);
    // head = DeleteAtIndex(head,1);
    // cout<<"after deletion At between :- "<<endl;
    // trivarsal(head);
    // head = DeleteAtLast(head);
    // cout << "after deletion At last :- " << endl;
    // trivarsal(head);
    return 0;
}