C++primer plus第六版课后编程题答案16.6

main166.cpp

queue的说明请看：http://www.360doc.com/content/13/0912/17/3373961_314003806.shtml

#include <iostream>
#include <queue>
#include <cstdlib>
#include <ctime>
using namespace std;
//我懒得分开多个了，直接从前面的复制过来了
class Customer
{
private:
long arrive;
int processtime;
public:
Customer(){arrive=processtime=0;};
void set(long when){
processtime=rand()%3+1;
arrive=when;
}
long when()const{
return arrive;
}
int ptime()
{
return processtime;
}
friend ostream&operator<<(ostream &os,const Customer &c)//用于检测
{
static int j=0;
os<<j++<<" arrive:"<<c.arrive<<" need time:"<<c.processtime<<endl;
return os;
}
};

typedef Customer Item;

const int MIN_PER_HR=60;
bool newCustomer(double x)//每隔x次，rand()/RAND_max会有一次值<1
{
return rand()*x/RAND_MAX<1;
}
void main166()
{
srand(time(0));//初始化rand();
cout<<"Case Study:Bank of Heather Automatic Teller"<<endl;
cout<<"Enter maximum size of queue:";
int qs;
cin>>qs;
queue<Item> line;//queue模板没有大小一说

cout<<"Enter the number of simulation hours:";
int hours;
cin>>hours;
long cyclelimit=MIN_PER_HR*hours;//循环的分钟数

cout<<"Enter the average number of customers per hour:";//一个小时来的人数
double perhour;
cin>>perhour;
double min_per_cust;
min_per_cust=MIN_PER_HR/perhour;//平均多少分钟来一个人

Item temp;
long turnaways=0;
long customers=0;
//long served=0;
long served=0;
long sum_line=0;
int wait_time=0;
long line_wait=0;

for(int cycle=0;cycle<cyclelimit;cycle++)//cycle每循环一次，代表过了一分钟
{
//line.s();
if(newCustomer(min_per_cust))
{
if(line.size()==qs)//这样就代表满了
turnaways++;//拒绝服务？？？//恩,应该就是拒绝服务的人数
else
{
customers++;//队列人数//应该是顾客人数+1而不是队列人数+1
temp.set(cycle);//cycle是到达时间
line.push(temp);//入队列

}

}
if(wait_time<=0&&line.size()!=0)//用户处理完了业务
{
line.pop();//出队列，不会返回值
//cout<<"after the delete"<<line;//test
wait_time=temp.ptime();//wait_time是该客户处理业务所用时间
line_wait+=cycle-temp.when();//cycle-temp.when();是该客户一共在队列中等了多久
//一开始wait_time初始化是0，然后进入这里之后，又重新设置了使其=processtime
//line_wait是该队列一共等了多久？？哦，应该是所有客户的等待时间
//line_wait是客户等待总时间
served++;//服务人数+1
}

if(wait_time>0)//正在处理业务的处理时间-1，因为过了一分钟
wait_time--;//话说这wait_time是谁设置了？一直=0？
//wait_time=temp.ptime()这里随机设置了wait-time
sum_line+=line.size();//sum_line又是神马东东？？
//sum_line是队伍总长度，每分钟计算一次队伍长度
}

if(customers>0)
{
cout<<"customers accepted:"<<customers<<endl;
cout<<" customers served:"<<served<<endl;
cout<<" turnaways:"<<turnaways<<endl;
cout<<"average queue size:";
cout.precision(2);
cout.setf(ios_base::fixed,ios_base::floatfield);
cout<<(double)sum_line/cyclelimit<<endl;
cout<<"average wait time:"<<(double)line_wait/served<<" minutes"<<endl;
}//我机器上面是18人最接近1分钟，队列长度10,时间100
else
cout<<"No coustomer!"<<endl;
cout<<"Done!"<<endl;
system("pause");
}