Question

好的，所以分配是从名为tickets.txt的文件中获取输入，并输出售出的门票总数以及总收入。文本文件中的值输入两列（1）售出的票数，以及（2）每种票类的价格。

文本文件如下：

这是我想出的代码......

#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;

/* Program Name:  Ticket_Sales.cpp
 * Date: May 2, 2018
 * Purpose: Calculate Total Ticket Sales
 */

int main() {

    {
        ifstream inFile;
        float ticket_cost;
        float tickets_sold;
        float total_cost ;
        float total_sold ;
        float ticket_revenue;

        /*
         * I noticed someone doing something similar to this on StackExchange; seems absolutely brilliant to include
         * a manner to check if the program is accessing the file.
         */
        inFile.open("C:\\Users\\pinkp\\CLionProjects\\M05_Ticket_Sales\\tickets.txt");
            if (inFile.fail()) {
                cout << "Failed to open the file." << endl;
                cin.get ();
                return 1;
            }

        while(inFile >> tickets_sold >> ticket_cost) {
                total_sold += tickets_sold;
                total_cost += ticket_cost;
                ticket_revenue = (total_cost * total_sold);

        }
        cout << fixed << setprecision(2);
        cout << "Total Tickets Sold:  " << total_sold << "." << endl;
        cout << "Total Revenue:  " << ticket_revenue << "." << endl;
    }
    /*
     * The value continues to return 2 less than the intended output, and I cannot pinpoint the exact cause.
     */
    return 0;
}

但是我对ticket_revenue的输出继续给我37506248.00，当手动将数字输入计算器时会给你37506250.00。两个数字的差异。我想过要做一个＆＃39; + 2＆＃39;把它弄到正确的数字，但我认为我的教授会对此不以为然。

无论ticket.txt中的数字是什么（我已经改变了几次），它总是比我期望的少两个。这是一些超级简单的C ++或编程概念吗？我曾经错过了什么？

谢谢！

Answer 1

您无法初始化ticket_revenue - 并查看其分配方式：

            ticket_revenue = (total_cost * total_sold);

这会使用总出售的门票数量和所有价格的总和的产品覆盖ticket_revenue。

你需要像（未经测试的）：

    unsigned long total_sold = 0;
    unsigned long ticket_revenue = 0;
    while (inFile >> tickets_sold >> ticket_cost) {
            auto transaction_revenue = tickets_sold * ticket_cost;
            total_sold += tickets_sold;
            ticket_revenue += transaction_revenue;
    }

BTW，don't use floating-point types for currency calculations！

这是代码的一个版本，修复了上述错误，没有外部输入文件（因此它代表Minmal, Complete and Verifiable Example）：

#include <iostream>
#include <vector>

int main()
{
    static const
        std::vector<std::pair<int, long>> sales =
        {{ 250, 5750 },
         { 100, 28000 },
         { 50, 35750 },
         { 25, 18750 } };

    long total_sold = 0;
    long ticket_revenue = 0;

    for (auto& sale: sales) {
        int tickets_sold = sale.first;
        long ticket_cost = sale.second;
        total_sold += tickets_sold;
        ticket_revenue += tickets_sold * ticket_cost;
    }

    std::cout << "Total Tickets Sold:  " << total_sold << ".\n";
    std::cout << "Total Revenue:  " << ticket_revenue << ".\n";
}

这会产生正确的答案：

Total Tickets Sold:  425.
Total Revenue:  6493750.

Answer 2

我认为相反

    while(inFile >> tickets_sold >> ticket_cost) {
            total_sold += tickets_sold;
            total_cost += ticket_cost;
            ticket_revenue = (total_cost * total_sold);

    }

你应该写

    ticket_revenue = 0;

    while(inFile >> tickets_sold >> ticket_cost) {
       ticket_revenue += ticket_sold * ticket_cost;
    }

否则，您总结门票数量和门票费用，您应该获得更大的价值。

C ++编程：分配的输出是边缘关闭的

2 个答案: