6.Double ended queue(DS)

#include<conio.h>
#include<stdio.h>
#define max 100
#define pf printf
#define sf scanf_s
typedef struct
{
    int q[max];
    int r,f;
}queue;
int isempty(queue *t)
{
    if(t->r==t->f)
        return 1;
    else
        return 0;
}
void insertleft(queue *t,int ele)
{
    if(t->f==-1)
    {
        pf("\nDequeue Overflow\n");
        return ;
    }
    t->q[t->f] =  ele;
    t->f--;
    return ;
}
void insertright(queue *t,int ele)
{
    if(t->r==max-1)
    {
        pf("\nDequeue Overflow\n");
        return ;
    }
    t->r++;
    t->q[t->r]=ele;
    return ;
}
void deleteleft(queue *t)
{
    int z;
    if(isempty(t))
    {
        pf("\nDequeue Underflow\n");
        return ;
    }
    z = t->q[t->f+1];
    t->f++;
    pf("\nDeleted element is %d",z);
    return ;
}
void deleteright(queue *t)
{
    int z;
    if(isempty(t))
    {
        pf("\nDequeue Underflow\n");
        return ;
    }
    z = t->q[t->r];
    t->r--;
    pf("\nDeleted element is %d",z);
    return ;
}
void display(queue *t)
{
    int i;
    if(isempty(t))
    {
        pf("\nDequeue is empty\n");
        return ;
    }
    pf("\nElements of Dequeue is given Below\n");
    for(i=t->f+1;i<=t->r;i++)
    {
        pf("%d\t",t->q[i]);
    }
    return ;
}
int main()
{
    int ch,ele;
    queue x;
    x.r=x.f=max/2;
    pf("\nIMPLEMENTATION OF DEQUEUE\n");
    while(1)
    {
        pf("Enter Choice \n1.Insertleft 2.Insertright 3.Deleteleft 4.Deleteright 5.Display 6.exit\t");
        sf("%d",&ch);
        if(ch==6)
            break;
        else
        {
            switch(ch)
            {
            case 1:pf("\nEnter element to be insert\n");
                sf("%d",&ele);
                insertleft(&x,ele);
                break;
            case 2:pf("\nEnter element to be insert\n");
                sf("%d",&ele);
                insertright(&x,ele);
                break;
            case 3:deleteleft(&x);
                break;
            case 4:deleteright(&x);
                break;
            case 5:display(&x);
                break;
            default:pf("\nInvalid choice\n");
            }
        }
    }
    _getch();
    return 0;
}