C++ program to implement the double ended queue using a double linked list

#include<iostream>
#include<conio.h>
#include<stdlib.h>
using namespace std;
 
class node
{
public:
int data;
class  node *next;
class node *prev;
};
 
class dqueue: public node
{
node *head,*tail;
int top1,top2;
public:
dqueue()
{
top1=0;
top2=0;
head=NULL;
tail=NULL;
}
void push(int x){
node *temp;
int ch;
if(top1+top2 >=5)
{
cout <<"dqueue overflow";
return ;
}
if( top1+top2 == 0)
{
head = new node;
head->data=x;
head->next=NULL;
head->prev=NULL;
tail=head;
top1++;
}
else
{
cout <<" Add element 1.FIRST 2.LAST\n enter ur choice:";
cin >> ch;
 
 
if(ch==1)
{
top1++;
temp=new node;
temp->data=x;
temp->next=head; 
temp->prev=NULL;
head->prev=temp;
head=temp;
}
else
{
top2++;
temp=new node;
temp->data=x;
temp->next=NULL;
temp->prev=tail;
tail->next=temp;
tail=temp;
}
 
}
}
void pop()
{
int ch;
cout <<"Delete 1.First Node 2.Last Node\n Enter ur choice:";
cin >>ch;
if(top1 + top2 <=0)
{
cout <<"\nDqueue under flow";
return;
}
if(ch==1)
{
head=head->next;
head->prev=NULL;
top1--;
}
else
{
top2--;
tail=tail->prev;
tail->next=NULL;
}
}
 
void display()
{
int ch;
node *temp;
cout <<"display from 1.Staring 2.Ending\n Enter ur choice";
cin >>ch;
if(top1+top2 <=0)
{
cout <<"under flow";
return ;
}
if (ch==1)
{
temp=head;
while(temp!=NULL)
{
cout << temp->data <<" ";
temp=temp->next;
}
}
else
{
temp=tail;
while( temp!=NULL) 
{
cout <<temp->data << " ";
temp=temp->prev;
}
}
}
};
 
main()
{
dqueue d1;
int ch;
while (1){
cout <<"1.INSERT  2.DELETE  3.DISPLAU  4.EXIT\n Enter ur choice:";
cin >>ch; 
switch(ch)
{
case 1:     cout <<"enter element";
cin >> ch;
d1.push(ch); break;
case 2: d1.pop(); break;
case 3: d1.display(); break;
case 4: exit(1);
}
}}