Circular queue size, help me please !!

[Suzanne90]

Dear all,
I am implementing a circular queue, but I can't find the formula to obtain the size of the queue; this one doesn't work correctly and gives me wrong results:

int size = abs (m_tail - m_front) ;

where m_front and m_tail are the indexes of the queue's front and tail respectively.

Please help me solve this issue :(

[Aceix]

can you show the code?

EDIT:

This worked for me. very similar:

#include <iostream>

using namespace std;

int main()
{
	int absolute;
	int first,last;
	
	cout<<"Enter a big number: ";
	cin>>first;
	cout<<"Enter another one(smaller): ";
	cin>>last;
	absolute=abs(first-last);
	cout<<"Absolute: "<<absolute;
	cin.ignore();
	cin.get();
}

[Suzanne90]

Thanks for the reply. Here the class Circular_Queue as I have implemented:

#include "circular_queue.h" 
#include <iostream> 
#include <cstdlib> 

#define MaxSize 150000   // in bytes, which means 100 packets maximum 

using namespace std ; 

typedef unsigned char Byte ; 

 CircularQueue::CircularQueue() 
{

   m_front = 0 ; 

   m_tail = 0 ; 


 }

  CircularQueue::~CircularQueue() 
{

}

void CircularQueue::insert(Byte byte) 

{ 

    if (m_front == (m_tail + 1) % MaxSize)

     { 
      // cout << "Circular Queue is full" << endl ; 

     }

    else 

     {
        m_tail = (m_tail + 1) % MaxSize ; 

        m_array[m_tail] = byte ; 

     }

}

Byte CircularQueue::dequeue(void) 

{ 
    Byte byte  ; 

   if (m_front == m_tail) 

    {  
       //cout << "the circular queue is empty" << endl ; 

    }

   else 

     { 
         byte = m_array[m_front] ; 

         m_front = (m_front + 1) % MaxSize ; 

       }
  
          return byte ; 

}

int CircularQueue::Size(void) 

{
   int size = abs(m_front – m_tail) ; 

   return  size  ; 
}

bool CircularQueue::isEmpty(void) 

{
   if (m_front == m_tail) 

      return true ; 

   else

      return false ; 
}

bool CircularQueue::isFull(void) 

{
    if ((m_front == m_tail + 1) % MaxSize) 

      return true ; 

    else 
    
      return false ; 

}

I have a problem with the function Size() which gives me a wrong result. Is there a general formula to get the circular queue size? Thanks in advance

[Suzanne90]

Thank you for the code snippet but it doesn't seem to be the same case since what you are implementing is not a circular queue. By definition, in a circular queue, the front and tail indexes are set to zero when they reach the max_size , which is expressed here by a modulo. May be I don't explain my problem correctly but your code does simply calculate the difference between two numbers and shows the result, doesn' it??

[Aceix]

Is circular queue a topic, hahaha lol! I'm still learning not a pro at all. but I do my best to help!

[ne555]

int size = abs (m_tail - m_front) ; ¿why do you use abs()? ¿when that value could be negative?

By the way

/*   if (m_front == m_tail) 
      return true ; 
   else
      return false;*/
   return m_front == m_tail;