c++ - 有人能告诉我为什么我的 for() 循环不会一直计数吗？

Question

我从命令行参数中读入，它们如下:

0.5 3 10 50 

maxClock 是最后一个参数，在本例中为 50。然后我有一个这样的 for 循环:

for(int k = 1; k < maxClock; k++)
{
    <code>
}

但是无论出于何种原因，我的程序都不会计数到 k。有时它只会数到 9，然后是 34，然后是 14，等等......我不知道发生了什么。有人可以给我另一种观点吗？

代码如下:

/* * 驱动.cpp

 *
 * This program simulates a bank with customers walking in for service and seeing tellers.
 * This program implements a classic Queue style system.
 *
 * Disclaimer:
 *
 *  - For some reason, the program will not run up until the time maxClock given in the command line arguments.
 *    This prevents the program from being able to print out the averageQueue length, maxQueueLength, etc at the
 *    bottom right after the for-loop.
 *
 *
 *
 */



////////////////////////////////////////////////////////////////////
///Includes///
////////////////////////////////////////////////////////////////////
#include <iostream>
#include <vector>
#include <cstdlib>
#include "Queue.h"
#include "Customer.h"
#include "QueueNode.h"
#include "Teller.h"

using namespace std;

int main(int argc, char *argv[])
{

    srand(time(NULL)); //seeds the random time generator

    if(argc != 5)
    {
        cout << "You must enter at least 5 command line arguments " << endl;
        exit(1);
    }

    /******************Command Line Args-Variables***************************/
    double p = atof(argv[1]);
    int numTellers = atoi(argv[2]); //number of the tellers (M)
    int maxService = atoi(argv[3]);
    int maxClock = atoi(argv[4]); //simulation time (N)

    /******************Local Variables***************************/
    int numberOfCustomers = 0;
    int serv;
    int randProb;
    int totalWait;
    unsigned long long AverageWaitTime;
    int customerWillBeFinished;
    int maxQLength;
    int counter;
    int AverageQueueLength;
    int wait;
    int individualWaitTime;
    int OtherThanK;
    int a = 10000;

    //Displays to user to double checks to make sure you entered in the arguments correctly
    cout << "------------------------------------------------------------" << endl;
    cout << "These are the arguments that you gave the program: " << endl;
    cout << endl;
    cout << "The p value is: " << p << endl;
    cout << "The number of tellers: " << numTellers << endl;
    cout << "The max service time is: " << maxService << endl;
    cout << "The max clock is: " << maxClock << endl;
    cout << endl;
    cout << "------------------------------------------------------------" << endl;
    cout << "\n";

    /******************Declaration of Queue & Vector***************************/
    Queue<Customer> line;
    vector<Teller> teller(numTellers);

    //loop to go through entire clock until the maxClock is reached
    for(int k = 1; k < maxClock; k++)
    {
        OtherThanK = k;
        randProb = ((rand() % 100) + 1); //generates a random number seeded with system time
        if(randProb < p*100)
        {
                serv = ((rand() % maxService) + 1); //generates a random number seeded with system time
                Customer customer(OtherThanK, serv); //passes in current time and service time (randomizeD)
                line.enqueue(customer); //pushes a customer onto the Queue.
                cout << "Customer arriving in queue at time: " << OtherThanK << endl;
        }
        customerWillBeFinished = serv + OtherThanK + 1;
        for(int i = 0; i < numTellers; i++)
        {
            if(teller[i].isFree() && (!line.isempty())) //checks to see if a teller is empty
            {
                cout << "Teller " << i << " is now free." << endl;
                Customer frontCustomer; //declares a customer called frontCustomer. This is the customer who is at the front of the Queue.
                line.dequeue(frontCustomer); //pulls off a customer from the Queue.
                wait = OtherThanK - frontCustomer.getArrivalTime();
                numberOfCustomers++; //increases by 1 each time through to keep tracking of the # of Customers.
                totalWait = totalWait + wait;
                cout << "Customer going to teller " << i << " at time " << frontCustomer.getArrivalTime() << endl; //retrieves arrival time
                cout << "This customer had to wait in line for " << wait << " minutes." << endl; //labs() is a function used to determine absolute value
                cout << "This customer will require " << serv << " minutes of service" << endl;
                teller[i].addCustomer(frontCustomer);
                line.remove(frontCustomer); //once cycled through, removes the customer from the Queue.

            }
        }
        cout << endl;
        cout << "Time is: "<< k << endl;
        cout << " \n Number of customers: " << numberOfCustomers << " " << "Total wait so far: " << std::labs(totalWait) << endl; //labs() is a function used to determine absolute value
    }

///////// WON'T PRINT ANY OF THIS OUT BECAUSE IT WONT EXIT LOOP ///////
    cout << "test" <<endl;
    AverageWaitTime = totalWait/numberOfCustomers;
    cout << "Average wait time is: " << AverageWaitTime*a << endl;
    maxQLength = line.getLength();
    cout << "The max Queue length is " << maxQLength << endl;
    AverageQueueLength = maxQLength/OtherThanK;
    cout << "The Average Queue Length is " << AverageQueueLength;
}

输出示例:(每次都变，这次统计到20):

------------------------------------------------------------
These are the arguments that you gave the program: 

The p value is: 0.5
The number of tellers: 3
The max service time is: 10
The max clock is: 50

------------------------------------------------------------

Max Clock is 50

Time is: 0

 Number of customers: 0 Total wait so far: 0
Max Clock is 50

Time is: 1

 Number of customers: 0 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 2
Teller 0 is now free.
Customer going to teller 0 at time 2
This customer had to wait in line for 0 minutes.
This customer will require 4 minutes of service

Time is: 2

 Number of customers: 1 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 3
Teller 1 is now free.
Customer going to teller 1 at time 3
This customer had to wait in line for 0 minutes.
This customer will require 10 minutes of service

Time is: 3

 Number of customers: 2 Total wait so far: 0
Max Clock is 50

Time is: 4

 Number of customers: 2 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 5
Teller 2 is now free.
Customer going to teller 2 at time 5
This customer had to wait in line for 0 minutes.
This customer will require 7 minutes of service

Time is: 5

 Number of customers: 3 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 6
Teller 0 is now free.
Customer going to teller 0 at time 6
This customer had to wait in line for 0 minutes.
This customer will require 2 minutes of service

Time is: 6

 Number of customers: 4 Total wait so far: 0
Max Clock is 50

Time is: 7

 Number of customers: 4 Total wait so far: 0
Max Clock is 50

Time is: 8

 Number of customers: 4 Total wait so far: 0
Max Clock is 50

Time is: 9

 Number of customers: 4 Total wait so far: 0
Max Clock is 50

Time is: 10

 Number of customers: 4 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 11
Teller 0 is now free.
Customer going to teller 0 at time 11
This customer had to wait in line for 0 minutes.
This customer will require 8 minutes of service

Time is: 11

 Number of customers: 5 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 12
Teller 2 is now free.
Customer going to teller 2 at time 12
This customer had to wait in line for 0 minutes.
This customer will require 5 minutes of service

Time is: 12

 Number of customers: 6 Total wait so far: 0
Max Clock is 50

Time is: 13

 Number of customers: 6 Total wait so far: 0
Max Clock is 50

Time is: 14

 Number of customers: 6 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 15
Teller 1 is now free.
Customer going to teller 1 at time 15
This customer had to wait in line for 0 minutes.
This customer will require 10 minutes of service

Time is: 15

 Number of customers: 7 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 16

Time is: 16

 Number of customers: 7 Total wait so far: 0
Max Clock is 50
Customer arriving in queue at time: 17
Teller 2 is now free.
Customer going to teller 2 at time 16
This customer had to wait in line for 1 minutes.
This customer will require 2 minutes of service

Time is: 17

 Number of customers: 8 Total wait so far: 1
Max Clock is 50

Time is: 18

 Number of customers: 8 Total wait so far: 1
Max Clock is 50

Time is: 19

 Number of customers: 8 Total wait so far: 1
Max Clock is 50

Time is: 20

 Number of customers: 8 Total wait so far: 1
Max Clock is 50
Customer arriving in queue at time: 21
Teller 0 is now free.
Customer going to teller 0 at time 21
This customer had to wait in line for 0 minutes.
This customer will require 10 minutes of service

Customer.h 类:

/*
 * Customer.h
 *
 */

#ifndef CUSTOMER_H_
#define CUSTOMER_H_

#include <iostream>
#include "QueueNode.h"
#include "Queue.h"
#include "Teller.h"
#include <cstdlib>

using namespace std;

class Customer
{

public:
    int serviceTime;
    int arrivalTime;
    Customer()
    {
        serviceTime = 0;
        arrivalTime = 0;
    }

    Customer(int arrival, int maxService)
    {
        arrivalTime = arrival;
        serviceTime = maxService;
    }

    int getServiceTime()
    {
        return serviceTime;
    }
    bool isDone()
    {
        serviceTime--;
        return serviceTime <= 0;
    }

    int getArrivalTime()
    {
        return arrivalTime;
    }
    void MinutePasses()
    {
        serviceTime--;
    }
};

#endif /* CUSTOMER_H_ */

Teller.h 类:

/*
 * 
 */

#ifndef TELLER_H_
#define TELLER_H_

#include <iostream>
#include "Customer.h"
#include "QueueNode.h"
#include "Queue.h"

using namespace std;

class Teller
{
private:
    //bool isOccupied;
    Customer customer;
protected:
    bool free;
public:
    Teller()
    {
        //isOccupied = false;
        free = true;
    }
    bool isFree()
    {
        //return free; - > B C
        if(!free)
        {
            customer.serviceTime--;
            if(customer.serviceTime == 0)
            {
                free = true;
                return true;
            }
            else return false;
        }
        {
            return true;
        }


    }

    void addCustomer(Customer C)
    {
        customer = C;
        free = false;
    }
    void CustMinutePasses()
    {
        if(!free)
        {
            customer.MinutePasses();
        }
    }
    Customer & getCustomer()
    {
        return customer;
    }
    void setAvailability(bool b)
    {
        free = b;
    }
    /*
    void setAvailability(bool b)
    {
        free = b;
    }
    */
};



#endif /* TELLER_H_ */

Answer 1

程序确实应该运行到 maxclock-1 (!)，除非它因为错误而崩溃(或挂起)。循环中没有其他条件，您似乎没有更改循环索引或边界。

当我使用我在 http://www.cplusplus.com/forum/general/71229/ 中找到的经过调整的队列实现来运行它时，它似乎可以正常工作。 .

由于您不提供队列实现，因此队列可能是错误的来源。

一个可能的原因:我注意到您然后移除 frontCustomer。作为出列的一部分，“我的”队列实现从队列中删除了第一个元素。我使用的原始队列实现没有提供 remove();由于您的方法需要一个参数，因此我假设它将使用默认的运算符==()在整个队列中搜索该特定元素。我不知道当该元素不存在时您的队列会做什么，尤其是当队列为空时。

@Damien Black:完全错了。请修复您的评论。你会因为它而在 comp.lang.c++ 上被贬低，cf。 https://groups.google.com/d/msg/comp.lang.c++/3d9ts9JuA-Q/6PtGSoXSIHQJ

C++ 按值传递，除非形式参数在函数签名中通过前缀 & 符号指定为引用。您可能会将语义与 C# 混淆。

虽然 C# 通过引用处理类，但这些引用是按值 (!) 传递的，除非您限定形参和实参“ref”。