// This program uses the a queue template to create a queue of strings.
#include <iomanip>
#include <iostream>
#include <cstdlib>
using namespace std;
//
// TO CREATE A "template" class named "T"
template <class T>
//
// TO CREATE A CLASS NAMED "Dynque"
class Dynque
{
private:
struct QueueNode
{
T value;
QueueNode *next;
QueueNode(T val, QueueNode *nextp = NULL)
{
value = val; next = nextp;
}
};
QueueNode *front;
QueueNode *rear;
int numItems;
public:
Dynque();
~Dynque();
//
// FUNCTION PROTOTYPE FOR "engueue"
// THE FUNCTION DOES NOT RETURN DATA
// THE PARAMETER LIST CONTAINS "T"
void enqueue(T);
// FUNCTION PROTOTYPE FOR "dequeue"
// THE FUNCTION DOES NOT RETURN DATA
// THE PARAMETER CONTAINS "T" PASSED BY REFERENCE
void dequeue(T &);
//
//
bool isEmpty();
bool isFull();
void clear();
};
// Constructor
template <class T>
Dynque<T>::~Dynque()
{
front = NULL;
rear = NULL;
numItems = 0;
}
// Destructor
template <class T>
Dynque<T>::Dynque()
{
clear();
}
// Function enqueue inserts the value in val
// at the rear of the queue.
template <class T>
void Dynque<T>::enqueue(T val)
{
if (isEmpty())
front = rear = new QueueNode(val);
else
{
rear->next = new QueueNode(val);
rear = rear->next;
}
numItems++;
}
// Function dequeue removes the value at the
// front of the queue, and copies it into val.
template <class T>
void Dynque<T>::dequeue(T &val)
{
QueueNode *temp;
if (isEmpty())
{
cout << "The queue is empty.\n";
exit(1);
}
else
{
// queue is not empty
//
// ASSIGN THE NUMBER AT THE FRONT OF THE LIST
// TO THE VARIABLE "val"
val = front ->value;
//
temp = front;
front = front->next;
delete temp;
numItems--;
}
}
// Function isEmpty returns true if the queue
// is empty, and false otherwise.
template <class T>
bool Dynque<T>::isEmpty()
{
if (numItems)
return false;
else
return true;
}
// Function clear dequeues all the elements
// in the queue. *
template <class T>
void Dynque<T>::clear()
{
T value; // Dummy variable for dequeue
while(!isEmpty())
dequeue(value);
}
int main()
{
Dynque<string> queue;
cout << " ";
cout << "This program uses a queue to store string data.\n\n";
cout << "ENTERING STRINGS IN THE QUEUE.";
//
// Enqueue 4 strings.
cout << "\nEnter 4 strings to enqueue:\n\n" ;
for (int x = 1; x <= 4; x++)
{
string value;
cout << "Enter string "<< x << ": ";
cin >> value;
//
// ADD A VALUE TO THE QUEUE
queue.enqueue( value );
}
cout << "\nREMOVING THE STRINGS FROM THE QUEUE.";
// Deqeue and retrieve all items in the queue
cout << "\nThe strings in the queue were:\n";
cout << "\n";
while (!queue.isEmpty())
{
string value;
//
// DELETE A VALUE FROM THE QUEUE
//queue.dequeue(value);
cout << "Removing " << value << endl;
}
cout << "\n\n";
system("pause");
return 0;
}
I can't figure what that error means. It compiles but when I try to run it gives me an error.
