queue.cpp

/**
 * @file queue.cpp
 * Implementation of the Queue class.
 *
 */

/**
 * Adds the parameter object to the back of the Queue.
 *
 * @param newItem object to be added to the Queue.
 */
template <class T> void Queue<T>::enqueue(T const &newItem)
{
    stack_1.push(newItem);
}

/**
 * Removes the object at the front of the Queue, and returns it to the
 * caller.
 *
 * @return The item that used to be at the front of the Queue.
 */
template <class T> T Queue<T>::dequeue()
{
   if (stack_2.isEmpty()) {
       while (!stack_1.isEmpty()) {
           stack_2.push(stack_1.pop());
       }
   }
   return stack_2.pop(); 
}

/**
 * Adds an element to the ordering structure.
 *
 * @see OrderingStructure::add()
 */
template <class T> void Queue<T>::add(const T &theItem)
{
    enqueue(theItem);
}

/**
 * Removes an element from the ordering structure.
 *
 * @see OrderingStructure::remove()
 */
template <class T> T Queue<T>::remove()
{
   return dequeue();
}

/**
 * Finds the object at the front of the Queue, and returns it to the
 * caller. Unlike dequeue(), this operation does not alter the queue.
 *
 * @return The item at the front of the queue.
 */
template <class T> T Queue<T>::peek()
{
    if (stack_2.isEmpty()) {
        while (!stack_1.isEmpty()) {
            stack_2.push(stack_1.pop());  
        }
    }
    return stack_2.peek();
}

/**
 * Determines if the Queue is empty.
 *
 * @return bool which is true if the Queue is empty, false otherwise.
 */
template <class T> bool Queue<T>::isEmpty() const
{
    return stack_1.isEmpty() && stack_2.isEmpty();
}