DS - LINKED LISTS 2

Write a C program to insert an element to the front end, rear end or specified position in the singly linked list also write the display function to display the content of the list and delete function to delete the node.

#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>
int i;

struct student
{
    int data;
    struct student *next;
};
typedef struct student *NODE;

NODE insert_front(NODE first,int d)
{
    NODE temp;
    temp=(NODE)malloc(sizeof(struct student));
    temp->data=d;
    temp->next=first;
    return temp;
}
NODE insert_rear(NODE first,int d)
{
    NODE temp,cur;
    temp=(NODE)malloc(sizeof(struct student));
    temp->data=d;
    temp->next=NULL;
    cur=first;
    while(cur->next!=NULL)
    cur=cur->next;
    cur->next=temp;
    return first;
}
NODE insert_pos(NODE first, int d,int pos)
{
    NODE temp,cur,prev;
    temp=(NODE)malloc(sizeof(struct student));
    temp->data=d;
    temp->next=NULL;
    if(first==NULL)
        return temp;
    cur=first;
    for(i=1;i<pos;i++)
    {
        prev=cur;
        cur=cur->next;
    }
    prev->next=temp;
    temp->next=cur;
    return first;
}
NODE delete(NODE first, int a)
{
    NODE temp,cur,prev;
    if(a==0)
    {
        cur=first;
        while(cur->next!=NULL){
        prev=cur;
        cur=cur->next;}
        prev->next=NULL;
        free(cur); return first;
    } else{
    cur=first;
    for(i=1;i<a;i++){
    prev=cur;
    cur=cur->next;}

    temp=cur->next;
    printf("\n ::: deleted is %d :: \n",cur->data);
    prev->next=temp;
    free(cur);
    return first;
}
}
void display(NODE first)
{
    NODE temp;
  if(first==NULL)
    printf("\nList is empty");
else{
    temp=first;
    printf("\n content is :: \n");
 while(temp!=NULL)
      {
       printf("%d\n",temp->data);
       temp=temp->next;
      }
}
}
void main()
{
    NODE first=NULL;
    int ch,d,pos;
    for(;;)
    {
        printf("\n 1.front insert \n 2.rear insert \n 3.pos insert \n 4. front delete ");
        printf("\n 5.rear delete \n 6.pos delete \n 7. display \n 8.exit \n");
        scanf("%d",&ch);
        switch(ch)
        {
            case 1: printf(" \n enter the item to be inserted :: \n"); scanf("%d",&d);
                first=insert_front(first,d); break;
            case 2: printf(" \n enter the item to be inserted :: \n"); scanf("%d",&d);
                first=insert_rear(first,d); break;
            case 3: printf(" \n enter the item to be inserted :: \n"); scanf("%d",&d);
                printf(" \n enter the position :: \n"); scanf("%d",&pos);
                first=insert_pos(first,d,pos); break;
            case 4: printf(" \n deleting item from front end \n");
                first=delete(first,1); break;
            case 5: printf(" \n deleting item from rear end \n");
                first=delete(first,0); break;
            case 6: printf(" \n enter the pos :: \n"); scanf("%d",&pos);
                printf(" \n deleting item from specified pos \n");
                first=delete(first,pos); break;
            case 7: printf(" \n content of linked list is ::: \n");
                display(first); break;
            case 8:exit(0); break;
        }   
    }
}