C++Primer Plus 第12章 类和动态内存分配::队列模拟----链表，堆栈，链表的方法的理解002

头文件定义Customer类，Queue类

//queue.h -- interface for a queue
#ifndef QUEUE_H_
#define QUEUE_H_
//This queue will contain Customer items
class Customer
{
   
private:
	long arrive;		//arrival time for customer ,到达时间
	int processtime;	//processing time for customer排队时间
public:
	Customer() {
    arrive = processtime = 0; }
	void set(long when);
	long when()const {
    return arrive; }
	int ptime()const {
    return processtime; }
};

typedef Customer Item;

class Queue
{
   
private:
	//class scope definitions
	//Node is a nested structure definition local to this c 
	struct  Node{
   Item item;struct Node* next;};
	enum {
   <