c++ - 简单程序 - 菜单只显示一次

Question

我正在尝试跟踪购买杂货的总量。

在我的程序中，每次我购买苹果、奶酪或面包时，程序都应该继续显示菜单。

但它一直在问“有多少个苹果？”在程序已经计算出苹果的总数之后，而不是返回菜单选择另一个项目。

可能与我使用的循环类型有关。

我一直在努力解决这个问题。任何帮助，将不胜感激。

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

int main()
{
     double BUDGET;
     const double apple= .60;
     const double lb_cheese= 1.60;
     const double loaf_bread = 2.50;

     double total;
     int count;
     char choice;
     double amount_left;

    cout <<"Welcome! What is the budget for your picnic lunch?"<< endl;
    cin>> BUDGET;

    cout<<"Choose one of the following"<<endl;
    cout<<"-------------------------------------"<<endl;
    cout<<"            MENU             \n "<<endl;
    cout<<"A-Apple      B-Cheese        C-Bread"<<endl;
    cout<<" $0.60       $1.50             $2.50       "<<endl;
    cout<<"-------------------------------------"<<endl;
    cin>> choice;



   while ((choice != 'Q') && (total <BUDGET)) //Q is the sentinel value to "quit" the  program
 {


    switch(choice)

  {

    case 'A':
    case 'a':

    cout<<"How many apples?";
    cin>> count;
    total+= (count *apple);
    break;



    case 'B':
    case 'b':

    cout<<"How many pounds of cheese ?";
    cin>> count;

    total+= (count* lb_cheese);
    break;



    case 'C':
    case 'c':
    cout<<"How many loafs of bread?";
    cin>> count;
    total+= (count * loaf_bread);
    break;



    default:
    cout<<"The entry you have entered is not valid, please try again."<<endl;
  }




if( total > BUDGET)
    { cout<<"You have exceeded your budget please check your cart.\n\n";
       break;
       }



cout<<"Your total is: $"<<setprecision((2))<<fixed<<total<<endl;
amount_left= BUDGET-total;
cout<<"You have $"<<setprecision(2)<<fixed<<amount_left<<" left to spend."<<endl;



 }

    return 0;
}

Answer 1

显示菜单不在循环中:

display menu
read option
while (option != quit) {
    do some calculations
}

因此菜单只显示一次。您可以将其更改为无限循环:

while (true) {
    display menu
    read option

    if (choice == 'Q' || total >= BUDGET)
        break;

    do some calculations
}

同时尽量避免编写超过 50 行的函数，将一些逻辑放在一些不同的函数中并调用这个函数，将其分解成更小的部分，这样会更容易阅读，也更容易理解。