LinkedList34.c

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

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

typedef struct node NODE;
typedef struct node* PNODE;
typedef struct node** PPNODE;

void InsertFirst(PPNODE First, PPNODE Last, int iNo)
{
    PNODE newn = NULL;

    newn = (PNODE)malloc(sizeof(NODE));

    newn->data = iNo;
    newn->next = NULL;

    if((*First == NULL) && (*Last == NULL) )
    {
        *First = newn;  
        *Last = newn;   
    }
    else
    {
        newn->next = *First;
        *First = newn;
    }
    (*Last)->next = *First;
}

void InsertLast(PPNODE First, PPNODE Last, int iNo)
{
    PNODE newn = NULL;

    newn = (PNODE)malloc(sizeof(NODE));

    newn->data = iNo;
    newn->next = NULL;

    if((*First == NULL) && (*Last == NULL) )
    {
        *First = newn;  
        *Last = newn;   
    }
    else
    {
        (*Last)->next = newn;
        *Last = newn;
    }
    (*Last)->next = *First;
}

void Display(PNODE First, PNODE Last)
{
   
    if((First == NULL) && (Last == NULL))
    {
        printf("Linked List is empty\n");
        return;
    }

    do {
        printf(" | %d | ->", First->data);
        First = First->next;
    } while (First != Last->next);
    printf("\n");
}

int main()
{
    
    PNODE Head = NULL;
    PNODE Tail = NULL;  

    Display(Head,Tail);

    InsertFirst(&Head,&Tail,51);
    InsertFirst(&Head,&Tail,21);
    InsertFirst(&Head,&Tail,11);

    InsertLast(&Head,&Tail,101);
    InsertLast(&Head,&Tail,111);
    InsertLast(&Head,&Tail,121);
    
    Display(Head,Tail);

    return 0;
}