初始化列表和基于范围的函数

Question

问题： 编写一个程序，提示用户输入一定数量的 1、2、5、10、20、50 和 100 美元钞票。分别向用户查询每个size Dollar的数量。

我认为我已经很好地完成了代码，但问题的最后一部分指出： 修改您的程序以使用向量的初始化列表，并使用基于范围的 for 语句来遍历向量。注意：这些 C++11 功能在 g++-4.6 和 Visual Studio 2012 中可用，但在其他编译器上可能不可用。

我不明白最后一部分在问什么。希望这里有人可以指出我正确的方向。这是一个 C++ 类，我的书没有最新版本。

对我的代码格式的任何批评也很棒！

这是我的代码：

 #include "std_lib_facilities_3.h"
    vector<int>bills;
    int bill;
    int bill_tot(){
        int sum = 

    1*bills[0]+2*bills[1]+5*bills[2]+10*bills[3]+20*bills[4]+50*bills[5]+100*bills[6];
            return sum;
        }
    int main()
    try{
        cout << "Enter the number of One Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");

        cout << "Enter the number of Two Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");

        cout << "Enter the number of Five Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");

        cout << "Enter the number of Ten Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");

        cout << "Enter the number of Twenty Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");

        cout << "Enter the number of Fifty Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");

        cout << "Enter the number of One Hundred Dollar Bills you have: ";
        cin >> bill;
        cout << '\n';
        bills.push_back(bill);
        if (bill<0)
            error("You can't have a negative value.\n");


        cout << "You have " << bills[0] <<" One Dollar Bills.\n";
        cout << "You have " << bills[1] <<" Two Dollar Bills.\n";
        cout << "You have " << bills[2] <<" Five Dollar Bills.\n";
        cout << "You have " << bills[3] <<" Ten Dollar Bills.\n";
        cout << "You have " << bills[4] <<" Twenty Dollar Bills.\n";
        cout << "You have " << bills[5] <<" Fifty Dollar Bills.\n";
        cout << "You have " << bills[6] <<" One Hundred Dollar Bills.\n";
        cout << "The value of all your Dollar Bills are $" << bill_tot() << endl;
        keep_window_open();
    }
    catch (runtime_error e) {   
        cout << e.what() << '\n';
        keep_window_open();
}

Answer 1

这是说明性代码：

std::vector<int> denomination { 1,2,5,20,50,100}; // Initializer list for vector
int sum = 0;
int number;
for ( int bill : denomination ) // range-based for loop
{
    cout << "Enter the number of $" << bill << " you have: ";
    cin >> number;
    sum += number * bill;
}