how do you implement a copy constructor for this pointer-based ADT
queue
#include <cassert // for assert
#include <new // for bad_alloc
using namespace std;
//private:{Queue::Queue(const Queue& Q)}
Queue::Queue() : backPtr(0), frontPtr(0)
{
} // end default constructor
Queue::Queue(const Queue& Q) throw(OutOfStorageException)
{
/////////// Implementation
here!!!!!!///////////////
} // end copy constructor
Queue::~Queue()
{
while (!isEmpty() )
{
dequeue();
} // end while
assert ( (backPtr == 0) && (frontPtr == 0) );
} // end destructor
bool Queue::isEmpty() const
{
return backPtr == 0;
} // end isEmpty
void Queue::enqueue(const QueueItemType& newItem)
throw(OutOfStorageException)
{
try
{
QueueNode *newPtr = new QueueNode;
newPtr->item = newItem;
newPtr->next = 0;
if (isEmpty() )
{
frontPtr = newPtr;
}
else
{
backPtr->next = newPtr;
} // end if
backPtr = newPtr;
}
catch(bad_alloc e)
{
throw OutOfStorageException("Memory allocation failed.");
} // end try/catch
} // end enqueue
void Queue::dequeue() throw(OutOfDataException)
{
if (isEmpty() )
{
throw OutOfDataException("Empty queue, cannot dequeue");
}
else
{ // queue is not empty; remove front
QueueNode *tempPtr = frontPtr;
if (frontPtr == backPtr) // special case?
{ // yes, one node in queue
frontPtr = 0;
backPtr = 0;
}
else
{
frontPtr = frontPtr->next;
} // end if
tempPtr->next = 0; // defensive strategy
delete tempPtr;
} // end if
} // end dequeue
void Queue::dequeue(QueueItemType& queueFront)
throw(OutOfDataException)
{
if (isEmpty() )
{
throw OutOfDataException("Empty queue, cannot dequeue");
}
else
{ // queue is not empty; retrieve front
queueFront = frontPtr->item;
dequeue(); // delete front
} // end if
} // end dequeue
void Queue::getFront(QueueItemType& queueFront) const
throw(OutOfDataException)
{
if (isEmpty() )
{
throw OutOfDataException("Empty queue, cannot getFront");
}
else
{
// queue is not empty; retrieve front
queueFront = frontPtr->item;
} // end if
} // end getFront
