p4.c

#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
#define MS 5
int c;
struct student
{
    char name[20],branch[20],usn[20],phon[20];
    int sem;
    float mark1,mark2,mark3,total,average;
    struct student*next;
    struct student*prev;
};
typedef struct student node;
int countnodes(node*head)
{
    node*p;
    p=head;
    c=0;
    while(p!=NULL)
    {
        p=p->next;
        c++;
    }
return c;
}
node*getnode()
{
    node*nn;
    nn=(node*)malloc(sizeof(node));
    printf("enter the details\n");
    printf("Name:\n");
    scanf("%s",nn->name);
     printf("Branch:\n");
    scanf("%s",nn->branch);
     printf("usn:\n");
    scanf("%s",nn->usn);
     printf("phone:\n");
    scanf("%s",nn->phon);
     printf("Sem:\n");
    scanf("%d",&nn->sem);
    printf("mark1,mark2,mark3\n");
    scanf("%f%f%f",&nn->mark1,&nn->mark2,&nn->mark3);
    nn->next=nn->prev=NULL;
    return nn;
}
node*display(node*head)
{
node*p;
if(head==NULL)

    printf("empty\n");

else
{
    p=head;
    printf("Name\tusn\t\tbranch\tphon\tsem\tmark1\tmark2\tmark3\ttotal\taverage\n");
    while(p!=NULL)
    {
        p->total=p->mark1+p->mark2+p->mark3;
        p->average=p->total/3;
        printf("%s\t%s\t%s\t%s\t%d\t%.2f\t%.2f\t%.2f\t%.2f\t%.2f\n",p->name,p->usn,p->branch,p->phon,p->sem,p->mark1,p->mark2,p->mark3,p->total,p->average);
        p=p->next;
    }
}
    printf("the number of node in a list %d",countnodes(head));

return head;
}
node*create(node*head)
{
    node*nn,*p;
  if(countnodes(head)==MS)
  {
      printf("full\n");
  }
  else if(head==NULL)
  {
      nn=getnode(head);
      head=nn;
  }
  else
  {
      p=head;
      nn=getnode(head);
      while(p->next!=NULL)
      {
          p=p->next;
      }
      p->next=nn;
      nn->prev=p;
  }
  return head;
}
node*insertfront(node*head)
{
    node*nn;
    if(countnodes(head)==MS)
    {
        printf("full\n");
    }
    
    
        
    
   else if(head=NULL)
    {
        nn=getnode(head);
        head=nn;
    }
    else
    {
        nn=getnode(head);
        nn->next=head;
        head->prev=nn;
        head=nn;
    }
    
    return head;
}
node*insertrear(node*head)
{
    if(countnodes(head)==MS)
    {
        printf("full\n");
    }
    else
    {
        head=create(head);
    }
    return head;
}
node*deletefront(node*head)
{
    node*p;
    if(head==NULL)
    {
        printf("full\n");
    }
    else if(countnodes(head)==1)
    {
        p=head;
        head=NULL;
        free(p);
    }
    else
    {
        p=head;
        ((head->next)->next!=NULL);
        head=head->next;
        p->next=NULL;
        free(p);
    }
    return head;
}
node*deleterear(node*head)
{
    node*p,*q;
    if(head==NULL)
    {
        printf("empty\n");
    }
    else if(countnodes(head)==1)
    {
        p=head;
        head=NULL;
        free(p);
    }
    else
    {
        p=head;
        while(p->next!=NULL)
        {
            p=p->next;
        }
        q=p->prev;
        q->next=NULL;
        p->prev=NULL;
        free(p);
    }
    return head;
}
void main()
{
    int i,n,ch;
    node*head;
    head=NULL;
    do
    {
        printf("\nMenu\t1.create\t2.display\t3.insertfront\t4.insertrear\t5.deletefront\t6.deleterear\t7.exit\n");
        printf("enter your choice\n");
        scanf("%d",&ch);
        switch (ch)
        {
            case 1:printf("entr the number of student\n");
            scanf("%d",&n);
            for(i=0;i<n;i++)
            head=create(head);
            break;
            case 2: head=display(head);
            break;
            case 3: head=insertfront(head);
            break;
            case 4: head=insertrear(head);
            break;
            case 5: head=deletefront(head);
            break;
            case 6: head=deleterear(head);
            break;
            case 7:exit(0);
            default:printf("invalid choice");

        }

    }while(ch>=1&&ch<=7);
}