C++ program to implement the Queue ADT using a single linked list

#include<iostream>
#include<conio.h>
#include<stdlib.h>
using namespace std;
class node
{
public:
class node *next;
int data;
};
 
class queue : public node
{
node *head;
int front,rare;
public:
queue()
{
front=-1;
rare=-1;
}
void push(int x)
{
if (rare < 0 )
{
head =new node;
head->next=NULL;
head->data=x;
rare ++;
}
else
{
node *temp,*temp1;
temp=head;
if(rare >= 4)
{
cout <<"queue over flow";
return;
}
rare++;
while(temp->next != NULL)
temp=temp->next;
temp1=new node;
temp->next=temp1;
temp1->next=NULL;
temp1->data=x;
}  }
 
void display()
{
node *temp;
temp=head;
if (rare < 0)
{
cout <<" queue under flow";
return;
}
while(temp != NULL)
{
cout <<temp->data<< " ";
temp=temp->next;
}
}
void pop()
{
node *temp;
temp=head;
if( rare < 0)
{
cout <<"queue under flow";
return;
}
if(front == rare)
{
front = rare =-1;
head=NULL;
return;
}
front++;
head=head->next;
}
};
main()
{
queue s1;
int ch;
while(1)
{
cout <<"\n1.PUSH\n2.POP\n3.DISPLAY\n4.EXIT\n enter ru choice:";
cin >> ch;
switch(ch)
{
case 1:
cout <<"\n enter a element";
cin >> ch;
s1.push(ch); break;
 
case 2: s1.pop();break;
case 3: s1.display();break;
case 4: exit(0);
}
}
return (0);
}