LinkedList

#include <iostream> 
using namespace std; 
// create a node using pointer
// pointer
struct node 
{ 
    int data; 
    node *next;
}; 

// creating nodes
class linked_list 
{ 
    protected: 
    node *head,*tail;
    static int objects ;
   
    public: 
linked_list() 
{ 
    head = NULL;
    tail = NULL; 
}
node* gethead() 
{ 
return head;
} 

// front of linked list

void front(int n) 
{ 
    node *tmp = new node;
    tmp -> data = n;
    tmp -> next = head; 
    head = tmp; 
    objects++;
} 

// abcksa fadsf paksdjlf kn
// alskdf lhasldkf 
void after(node *a, int value)
{ 
    node* p = new node; 
    p->data = value;
    p->next = a->next;
    a->next = p;
    objects++;
} 
void last(int n) 
{ 
    node *tmp = new node;
    tmp->data = n;
    tmp->next = NULL; 
    if(head == NULL) 
    { 
        head = tmp; 
        tail = tmp; 
    } 
    else
    { 
        tail->next = tmp;
        tail = tail->next;
    }
    objects++;
} 
void display_loop() 
{ 
    node *tmp;
    tmp = head; 
    while (tmp != NULL) 
    { 
        cout << tmp->data << endl;
        tmp = tmp->next; 
    } 
    cout << "NULL\n" << endl; 
} 
    static void display_rec(node *head) 
    { 
       if(head == NULL) 
      { 
    cout << "NULL" << endl; 
      } 
        else 
      { 
    cout << head->data << endl;
            display_rec(head->next);
      } 
    }        
void del(node *before_del) 
{ 
    node* temp;
    temp = before_del->next;
    before_del->next = temp->next;
    delete temp;
    objects--;
} 
    void del_first() 
    { 
        if (head) 
        { 
            node* temp = head;
            head = head->next;
            delete temp; 
        } 
        objects--;
    } 
    void del_last() 
    { 
        node* prev; 
        node* curr;
        if (head==NULL)
        { 
// empty list 
        } 
            else if (head->next==NULL)
            { 
                curr = head;
                head = NULL;
                delete curr; 
            }
            else
            { 
            curr = head;
            while(curr->next != NULL) 
            { 
                prev = curr; 
                curr = curr->next;
            } 
            prev->next = NULL; 
            delete curr;
            }
            objects--;
    }
    virtual void PUSH(int )
    {
        cout<<"PUSH  main";
    }
    virtual void POP()
    {
        cout << "POP main";
    }
    static void size( )
    {
        cout<<"The number of elements(size):" <<  objects << endl << endl ; 
        objects=0;
    } 
}; 
template <typename T>
class LinkStack:public linked_list
{
  public:
  void PUSH(T n)
  {
    node *tmp = new node;
    tmp -> data = n;
    tmp -> next = head; 
    head = tmp; 
    objects++;
  }
  void POP()
   { 
        if (head) 
        { 
            node* temp = head;
            head = head->next;
            delete temp; 
        } 
        objects--;
    } 
};
template <typename X>
class LinkQueue:public linked_list
{
  public:
  void PUSH(X n)
  {
    node *tmp = new node;
    tmp->data = n;
    tmp->next = NULL; 
    if(head == NULL) 
    { 
        head = tmp; 
        tail = tmp; 
    } 
    else
    { 
        tail->next = tmp;
        tail = tail->next;
    }
    objects++;
  }
  void POP()
   { 
        if (head) 
        { 
            node* temp = head;
            head = head->next;
            delete temp; 
        } 
        objects--;
    } 
};
int linked_list::objects=0;

int main() 
{ 
    linked_list *a;
    LinkStack <int>s;
    a=&s;                    //Polymorphism
    a->last(1);
    a->last(2); 
    a->front(3);
    a->front(4);
    a->PUSH(2);
    a->POP();
    a->POP();
    a->PUSH(3);
    linked_list::display_rec(a->gethead()); 
    a->size();
    LinkQueue <int>q;
    a=&q; //This is another list for Queue using linked list.
    a->last(1);
    a->front(1);
    a->PUSH(3);
    a->POP();
    linked_list::display_rec(a->gethead()); 
    a->size();
    return 0; 
}