circularQueue.cpp

class circularQueue
{
    int *data;
    int nextIndex;
    int firstIndex;
    int size;
    int capacity;

public:
    circularQueue(int s)
    {
        data = new int[s];
        nextIndex = 0;
        firstIndex = -1;
        size = 0;
        capacity = s;
    }

    int getSize()
    {
        return size;
    }

    bool isEmpty()
    {
        return size == 0;
    }

    // insert elements in the queue
    void enqueue(int element)
    {
        if (size == capacity)
        {
            cout << "Queue is Full " << endl;
            return;
        }
        data[nextIndex] = element;
        nextIndex = (nextIndex + 1) % capacity;
        if (firstIndex == -1)
        {
            firstIndex = 0;
        }
        size++;
    }

    int front()
    {
        if (isEmpty())
        {
            cout << "Queue is empty" << endl;
            return 0;
        }
        return data[firstIndex];
    }

    int dequeue()
    {
        if (isEmpty())
        {
            cout << "Queue is empty" << endl;
            return 0;
        }
        int ans = data[firstIndex];
        firstIndex = (firstIndex + 1) % capacity;
        size--;
        if (size == 0)
        {
            firstIndex = -1;
            nextIndex = 0;
        }
        return ans;
    }
};
int main()
{
    circularQueue c(20);
    c.enqueue(3);
    c.enqueue(5);
    c.enqueue(7);
    c.enqueue(9);
    c.dequeue();

    return 0;
}