#include <iostream>

#include <stdio.h>

#define QUEUE_UNDERFLOW 1;

using namespace std;

struct node

{

int item;

node *next;

};

class Queue

{

private:

node *front; // point to start node

node *rear; // point to last node

public:

Queue();

Queue(Queue &);

Queue &operator=(Queue &);

void insertElement(int);

int getRear();

int getFront();

void deleteFront();

int countElement();

~Queue();

};

Queue::Queue() // initially both node pointers containing null;

{

front = rear = NULL;

}

Queue::Queue(Queue &q)

{

front = rear = NULL;

node *r = q.front;

while (r != NULL)

{

insertElement(r->item);

r = r->next;

}

}

Queue &Queue::operator=(Queue &q)

{

while (front)

deleteFront();

node *r = q.front;

while (r != NULL)

{

insertElement(r->item);

r = r->next;

}

return *this;

}

void Queue::insertElement(int data)

{

node *n = new node; // prepare node

n->item = data;

n->next = NULL;

if (front == NULL) // if linked List is empty

{

front = n;

rear = n;

}

else // if linked list has one element or more

{

rear->next = n;

rear = n;

}

}

int Queue::getRear()

{

if (rear == NULL)

throw QUEUE_UNDERFLOW;

return rear->item;

}

int Queue::getFront()

{

if (front == NULL)

throw QUEUE_UNDERFLOW;

return front->item;

}

void Queue::deleteFront()

{

if (front == NULL)

{

throw QUEUE_UNDERFLOW;

}

else if (front->next == NULL) // or we can say that front == rear i.e list has only one element

{

delete front;

front = rear = NULL;

}

else

{

node *r = front;

front = front->next;

delete r;

}

}

int Queue::countElement()

{

if(front==NULL)

return 0;

else if(front->next == NULL)

return 1;

else

{

node *r = front;

int count=1;

while(r->next == NULL)

{

count++;

r = r->next;

}

return count;

}

}

Queue::~Queue()

{

while (front)

deleteFront();

}