Queue

#include<iostream>
using namespace std;
class Queue
{
    int data[10];
    int head;
    int tail;
public:
    Queue();
    void Enqueue(int dat);
    int Dequque();
};
Queue::Queue()
{
    head = tail = 0;
}
void Queue::Enqueue(int dat)
{
    int len = sizeof data / data[0];
    if (tail == len - 1)
        tail = 0;
    if (tail + 1 == head)
    {
        cout << "overflow"<<endl;
        return;
    }
    data[tail++] = dat;
        
}
int Queue::Dequque()
{
    int len = sizeof data / sizeof data[0];
    if (head == len - 1)
        head = 0;
    if (head == tail)
    {
        cout << "NULL" << endl;
        return -1;
    }
    return data[head++];
}
int main()
{
    Queue q;
    q.Enqueue(1);
    q.Enqueue(2);
    
    cout<<q.Dequque()<<endl;
    cout << q.Dequque()<<endl;
    cout << q.Dequque()<<endl;
    return 0;
}