C++机票费计算方案

Question

我必须创建一个计算机票费用的程序。到目前为止，这是一个简单的程序，我还没有完成对它的添加，但每次我运行它时，结果都是0。我的代码中是否遗漏了什么？我是一个初学者，我将感谢任何关于改进我的代码的建议。谢谢。

#include <iostream>
            using namespace std;

            void main () {

                int distance = 0;
                int num_bags= 0;
                int num_meals= 0;
                double distance_price = distance * 0.15;
                double bag_price = num_bags * 25.00;
                double meal_price = num_meals * 10.00;
                double total_airfare = 0.00;


            cout << "CorsairAir Fare Calculator" << endl;

            cout << "Enter the distance being travelled:  " << endl;
            cin >> distance;

            cout << "Enter number of bags checked:  " <<endl;
            cin >> num_bags;


            cout << "Enter the number of meals ordered:  " << endl;
            cin >> num_meals;


            total_airfare = (distance_price + bag_price + meal_price);


            cout << total_airfare;




            }

Answer 1

你的困惑是完全可以理解的--你遗漏的一点是，当你赋值一个变量时，你在那个时刻将左边赋值给右边的结果。这不像代数，你说f(x) = x + 5和f(x)总是x + 5是什么。

因此，当distance为0 (您刚刚初始化了它)时，您可以指定double distance_price = distance * 0.15。即使在您请求输入并更改distance之后，distance_price仍然是0。

在请求输入之后进行价格计算，一切都会正常工作。

Answer 2

您正在使用默认值(即0 )计算distance_price bag_price meal_price，而不是使用您从user获取的值。

下面的代码运行良好，你不会看到这个问题。

   #include <iostream>
    using namespace std;
    // My compiler did not allow void main so used int main
    int main () {

    int distance = 0;
    int num_bags= 0;
    int num_meals= 0;

    double distance_price ;
    double bag_price ;
    double meal_price;
    double total_airfare;

    cout << "CorsairAir Fare Calculator" << endl;

    cout << "Enter the distance being travelled:  " << endl;
    cin >> distance;

    cout << "Enter number of bags checked:  " <<endl;
    cin >> num_bags;


    cout << "Enter the number of meals ordered:  " << endl;
    cin >> num_meals;


    distance_price = distance * 0.15;
    bag_price = num_bags * 25.00;
    meal_price = num_meals * 10.00;
    total_airfare = 0.00;


    total_airfare = distance_price + bag_price + meal_price;


    cout << total_airfare;
    return 0;
    }

结果

CorsairAir Fare Calculator
Enter the distance being travelled:
200
Enter number of bags checked:
2
Enter the number of meals ordered:
2
100