循环对联实现, //1.创建空的循环队列,为结构体在堆区分配空间 //2.判断队列是否为空 //3.判断队列是否为满 //4.入队，操作rear //5.出对，操作front(Circular couplet implementation, //1. creates an empty loop queue that allocates space for the structure in the heap area //2. determines whether the queue