如何根据用户输入的数据在 C++/命令中正确排列小数点？在不应该的情况下也有四舍五入的问题

Question

我一直在研究这个学校提示：

编写一个 C++ 程序，要求用户输入每月因驾驶汽车而产生的以下费用：贷款支付、保险、汽油、机油、轮胎和维护。然后，该程序应显示这些费用的每月总费用，以及这些费用的预计年度总费用。

标记每项成本。标签应左对齐，列宽为 30 个字符。成本应右对齐并显示为小数点后两位，列宽为 15。

如果年度总额大于 1000 美元，则将年度总额的 10% 添加到年度总额中。

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

int main()

{
    double loan_Payment;
    double insurance;
    double gas;
    double oil;
    double tires;
    double maintenance;


    /// text setup
    cout.width(30); cout << left << "Loan Payment" << right << "$  " << fixed << setprecision(2);

    cout.width(15); cin >> right >> loan_Payment;

    cout.width(30); cout << left << "Insurance" << right << "   " << fixed << setprecision(2);

    cout.width(15); cin >> right >> insurance;

    cout.width(30); cout << left << "Gas" << right << "   " << fixed << setprecision(2);

    cout.width(15); cin >> right >> gas;

    cout.width(30); cout << left << "Oil" << right << "   " << fixed << setprecision(2);

    cout.width(15); cin >> right >> oil;

    cout.width(30); cout << left << "Tires" << right << "   " << fixed << setprecision(2);

    cout.width(15); cin >> right >> tires;

    cout.width(30); cout << left << "Maintenance" << right << "   " << fixed << setprecision(2);

    cout.width(15); cin >> right >> maintenance;

    // adding total.yearly total, 10%

    cout.width(30); cout << left << "Total" << right << "$  ";

    cout.width(15); cout << left << (loan_Payment + insurance + gas + oil + tires + maintenance) << fixed << setprecision(2) << endl;

    cout.width(30); cout << left << "Yearly Total" << right << "$  ";

    cout.width(15); cout << left << (12 * (loan_Payment + insurance + gas + oil + tires + maintenance)) << fixed << setprecision(2) << endl;

    
    //if yearly total is greater than 1000 add 10 percent of the yearly total
    double yearly_total;
    yearly_total = (12 * (loan_Payment + insurance + gas + oil + tires + maintenance));
    if (yearly_total >= 1000) 
    {
        cout.width(30); cout << left << "10%" << right << "$  ";
        cout.width(15); cout << left << (12 * (loan_Payment + insurance + gas + oil + tires + maintenance)) * .10 << fixed << setprecision(2) << left << endl;
        cout.width(30); cout << left << "Grand Total" << right << "$  " << left << ((12 * (loan_Payment + insurance + gas + oil + tires + maintenance)) * .10) + (12 * (loan_Payment + insurance + gas + oil + tires + maintenance)) << fixed << setprecision(2) << endl;

    }

        
}

我从该代码得到了这个输出：

Loan Payment                  $  303.28  
Insurance                        75.00
Gas                              125.00
Oil                              45.00
Tires                            0.00
Maintenance                      15.00
Total                         $  563.28
Yearly Total                  $  6759.36
10%                           $  675.94
Grand Total                   $  7435.30

但是我需要的输出是这样的：

Loan Payment               $   303.28
Insurance                       75.00
Gas                            125.00
Oil                             45.00
Tires                            0.00
Maintenance                     15.00
Total                      $   563.28
Yearly total               $  6759.36
10%                        $   675.93
Grand Total                $  7435.29

如您所见，输出并不完全匹配，因为小数位没有正确对齐。我不知道如何做到这一点，因为当我将输出的前半部分输入命令提示符时，它没有将它们排列起来，我也不知道如何将它设置到它所在的位置和后半部分。我也不明白为什么它会在总计和产出的 10% 部分四舍五入，也无法找出原因。任何帮助表示赞赏！

Answer 1

就个人而言，我会尝试将此代码放入 for 循环中并遍历一个包含这些数字的数组，这样您就不必一遍又一遍地重写打印语句，但如果这是您必须这样做的方式，只需删除第一组“固定”关键字，并可能将第二组 setw() 设置为 10 左右。

double loan_payment = 303.28, insurance = 75.00, gas = 125.00, oil = 45.00, tires = 0.00, maintenance = 15.00, total = 563.28;

cout << setw(30) << left << "Loan Payment" << right << "$" << setw(10) << right << fixed << setprecision(2) << loan_payment << endl;

cout << setw(30) << left << "Insurance" << right << "$" << setw(10) << right << fixed << setprecision(2) << insurance << endl;

cout << setw(30) << left << "Gas" << right << "$" << setw(10) << right << fixed << setprecision(2) << gas << endl;

cout << setw(30) << left << "Oil" << right << "$" << setw(10) << right << fixed << setprecision(2) << oil << endl;

cout << setw(30) << left << "Tires" << right << "$" << setw(10) << right << fixed << setprecision(2) << tires << endl;

cout << setw(30) << left << "Maintenance" << right << "$" << setw(10) << right << fixed << setprecision(2) << maintenance << endl;

cout << setw(30) << left << "Total" << right << "$" << setw(10) << right << fixed << setprecision(2) << (loan_payment + insurance + gas + oil + tires + maintenance)`