C++“自动售货机”任务

Question

任务：

编写一个程序，让用户选择你最喜欢的5种饮料(可乐，水，雪碧，……等等)。然后允许用户通过输入数字1-5来选择饮料.输出他们选择的饮料。★如果编程使用If语句而不是开关语句，则修改它以使用switch语句。如果您的程序使用开关语句，则修改它以使用If / modify语句。★★修改程序，以便如果用户输入的选择不是1-5，那么它将输出“Error.select无效，这是您的钱回来”。

#include <iostream>
using namespace std;

int main() {

int drink = 0;
string ifswitch;
string again = "y";


while( again == "y" || again == "Y")
{
    cout << "Would you like to use if or switch statements?: ";
    cin >> ifswitch;
    cout << endl;

    if(ifswitch == "switch" || ifswitch == "Switch")
    {
        cout << "Now using switch statements..." << endl << endl;

        cout << "Your choices of drinks are: " << endl;
        cout << "1 - Coke" << endl;
        cout << "2 - Sprite" << endl;
        cout << "3 - Water" << endl;
        cout << "4 - Orange Juice" << endl;
        cout << "5 - Apple Juice" << endl;

        cout << "What drink would you like (1/5): ";
        cin >> drink;
        cout << endl;

        switch(drink)
        {
            case 1 :
                cout << "You chose Coke." << endl;
                break;
            case 2 :
                cout << "You chose Sprite." << endl;
                break;
            case 3 :
                cout << "You chose Water." << endl;
                break;
            case 4 :
                cout << "You chose Orange Juice." << endl;
                break;
            case 5 :
                cout << "You chose Apple Juice." << endl;
                break;  
            default :
                cout << "Error. Choice was not valid, Here is your money back.";

        }   
    }
    else if(ifswitch == "if" || ifswitch == "If")
    {
        cout << "Now using if statements..." << endl << endl;

        cout << "Your choices of drinks are: " << endl;
        cout << "1 - Coke" << endl;
        cout << "2 - Sprite" << endl;
        cout << "3 - Water" << endl;
        cout << "4 - Orange Juice" << endl;
        cout << "5 - Apple Juice" << endl;

        cout << "What drink would you like (1/5): ";
        cin >> drink;
        cout << endl;

        if(drink == 1)
            cout << "You chose Coke." << endl;
        else if(drink == 2)
            cout << "You chose Sprite." << endl;
        else if(drink == 3)
            cout << "You chose Water." << endl;
        else if(drink == 4)
            cout << "You chose Orange Juice." << endl;
        else if(drink == 5)
            cout << "You chose Apple juice." << endl;
        else
        cout << "Error. Choice was not valid, Here is your money back.";        

    }   

    cout << "Would you like to go again? (Y/N)" << endl;
    cin >> again;
    cout << endl;

}

    cout << "Ending...";

}

Answer 1

这里有一种方法可以避免编写两个版本的指令，既不使用switch也不使用级联if：

#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>

static const std::vector<std::string> drinks = {
    "Coke",
    "Sprite",
    "Water",
    "Orange Juice",
    "Apple Juice"
};

void print_drinks(auto& o, std::vector<auto> drinks)
{
    int i = 0;
    for (auto drink: drinks)
        o << ++i << " - " << drink << "\n";
    o.flush();
}

int main()
{
    print_drinks(std::cout, drinks);

    std::cout << "What drink would you like? (1-" << drinks.size() << ")" << std::endl;
    size_t n;
    if (!(std::cin >> n) || !n || n > drinks.size()) {
        std::cerr << "Error. Choice was not valid, Here is your money back." << std::endl;
        return EXIT_FAILURE;
    }

    // We now have a valid selection
    const std::string drink = drinks[n-1];
    std::cout << "You chose " << drink << "." << std::endl;

    // Implicit EXIT_SUCCESS
}

我不建议你把这个作为你的家庭作业，但是你可以从学习中学到一些东西。

• 我们没有在任何需要的地方重复饮料的名字，而是把它们存放在一个地方。这确保了打印的菜单与选择后的输出之间的一致性(例如，在您的代码中，您有Apple Juice和Apple juice)。它还可以添加或删除饮料，而无需更改代码的任何“逻辑”部分。
• 按照“做好一件事”的理念，我已经把周围的循环取出来了。您可以很容易地使用shell来重复执行程序: while ./select_ done；do :；done或while；do ./select_done；done或do ./select_done；同时阅读-p“您还想再去吗？y/N”-N 1再次\& [ $again =~ [yY] ]。