C++ program to implement circular queue using array

#include <iostream.h>
class cqueue
{
	private :
		int *arr ;
		int front, rear ;
		int MAX;
	public :
		cqueue( int maxsize = 10 ) ;
		void addq ( int item ) ;
		int delq( ) ;
		void display( ) ;
} ;
cqueue :: cqueue( int maxsize )
{
	MAX = maxsize ;
	arr = new int [ MAX ];
	front = rear = -1 ;
	for ( int i = 0 ; i < MAX ; i++ )
		arr[i] = 0 ;
}
void cqueue :: addq ( int item )
{
	if ( ( rear + 1 ) % MAX == front )
	{
		cout << "\nQueue is full" ;
		return ;
	}
	rear = ( rear + 1 ) % MAX;
	arr[rear] = item ;
	if ( front == -1 )
		front = 0 ;
}
int cqueue :: delq( )
{
	int data ;
	if ( front == -1 )
	{
		cout << "\nQueue is empty" ;
		return NULL ;
	}
 
	data = arr[front] ;
	arr[front] = 0 ;
	if ( front == rear )
	{
		front = -1 ;
		rear = -1 ;
	}
	else
		front = ( front + 1 ) % MAX;
	return data ;
}
void cqueue :: display( )
{
	cout << endl ;
	for ( int i = 0 ; i < MAX ; i++ )
		cout << arr[i] << "  " ;
	cout << endl ;
}
void main( )
{
	cqueue a ( 10 ) ;
	a.addq ( 14 ) ;
	a.addq ( 22 ) ;
	a.addq ( 13 ) ;
	a.addq ( -6 ) ;
	a.addq ( 25 ) ;
	cout << "\nElements in the circular queue: " ;
	a.display( ) ;
	int i = a.delq( ) ;
	cout << "Item deleted: " << i ;
	i = a.delq( ) ;
	cout << "\nItem deleted: " << i ;
	cout << "\nElements in the circular queue after deletion: " ;
	a.display( ) ;
	a.addq ( 21 ) ;
	a.addq ( 17 ) ;
	a.addq ( 18 ) ;
	a.addq ( 9 ) ;
	a.addq ( 20 ) ;
	cout << "Elements in the circular queue after addition: " ;
	a.display( ) ;
	a.addq ( 32 ) ;
	cout << "Elements in the circular queue after addition: " ;
	a.display( ) ;
}

15 Responses to “C++ program to implement circular queue using array”

  1. there is no ‘queue is full’ concept in circular buffer. you need to modify ur code to rollover the rear piinter.

    Reply
    • in above comment i read that there is no concept of Full… but i run it There is concept of IS FULL… just type Int in place of void and run it,,,

      Reply
  2. nehemiah

    @ Dummy….Not necessary pal…There are many ways to look at it..
    If you ask me I will write 3 methods or one method with three modes

    – Enqueue Soft – Just tries to add element, fails if the queue is full
    – Enqueue Hard – Somehow adds the element by allocating extra memory
    – Enqueue Forced – This is what you are talking about, It simply adds the element by dropping the first element(dequeued)

    Reply
  3. nehemiah

    @ Author…Why don’t you templatize this program so that it can take any type of elements?

    Reply
  4. /*
    * C++ Program to Implement Circular Queue
    */
    #include
    #define MAX 5
    using namespace std;
    /*
    * Class Circular Queue
    */
    class Circular_Queue
    {
    private:
    int *cqueue_arr;
    int front, rear;
    public:
    Circular_Queue()
    {
    cqueue_arr = new int [MAX];
    rear = front = -1;
    }
    /*
    * Insert into Circular Queue
    */
    void insert(int item)
    {
    if ((front == 0 && rear == MAX-1) || (front == rear+1))
    {
    cout<<"Queue Overflow \n";
    return;
    }
    if (front == -1)
    {
    front = 0;
    rear = 0;
    }
    else
    {
    if (rear == MAX – 1)
    rear = 0;
    else
    rear = rear + 1;
    }
    cqueue_arr[rear] = item ;
    }
    /*
    * Delete from Circular Queue
    */
    void del()
    {
    if (front == -1)
    {
    cout<<"Queue Underflow\n";
    return ;
    }
    cout<<"Element deleted from queue is : "<<cqueue_arr[front]<<endl;
    if (front == rear)
    {
    front = -1;
    rear = -1;
    }
    else
    {
    if (front == MAX – 1)
    front = 0;
    else
    front = front + 1;
    }
    }
    /*
    * Display Circular Queue
    */
    void display()
    {
    int front_pos = front, rear_pos = rear;
    if (front == -1)
    {
    cout<<"Queue is empty\n";
    return;
    }
    cout<<"Queue elements :\n";
    if (front_pos <= rear_pos)
    {
    while (front_pos <= rear_pos)
    {
    cout<<cqueue_arr[front_pos]<<" ";
    front_pos++;
    }
    }
    else
    {
    while (front_pos <= MAX – 1)
    {
    cout<<cqueue_arr[front_pos]<<" ";
    front_pos++;
    }
    front_pos = 0;
    while (front_pos <= rear_pos)
    {
    cout<<cqueue_arr[front_pos]<<" ";
    front_pos++;
    }
    }
    cout<<endl;
    }
    };
    /*
    * Main
    */
    int main()
    {
    int choice, item;
    Circular_Queue cq;
    do
    {
    cout<<"1.Insert\n";
    cout<<"2.Delete\n";
    cout<<"3.Display\n";
    cout<<"4.Quit\n";
    cout<>choice;
    switch(choice)
    {
    case 1:
    cout<>item;
    cq.insert(item);
    break;
    case 2:
    cq.del();
    break;
    case 3:
    cq.display();
    break;
    case 4:
    break;
    default:
    cout<<"Wrong choice\n";
    }/*End of switch*/
    }
    while(choice != 4);
    return 0;
    }

    Reply
  5. the above code is correct 100%. just one mistake there , in void main( ). type int main () . then program will run correctly.. i run it .. it works with all operation like is Full , is Empty , Dequeue and enqueue etc.. it works all .. in c-Free or Dev

    Reply
  6. in above comment i read that there is no concept of Full… but i run it There is concept of IS FULL… just type Int in place of void and run it,,,

    Reply
  7. Dorsiflector

    I would not trust this code.
    It does not do what it claims: it is not a circular queue. A circular queue never gets “full,” it’s like a circle: it just keeps going around.

    Also, since we’re putting the data on the heap with the following statement:
    arr = new int [ MAX ];
    and it has no destructor, there is probably a memory leak.

    There’s probably more problems, but I look no further. The above is enough to lose my trust in this code.

    Reply
  8. pavithra.r

    i need array implementation queue program for following functions as arrayqueue(),enqueue(),dequeue(),front(),
    back().

    Reply

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