C++ C+中的输入验证+；

我正在编写一个需要输入验证的程序，如果单位小于或等于0，程序将不会运行，但我会不断获取包含总数的字符串，但如果值为0，我不会尝试运行该程序

//Write a program that asks for the numbers of units sold and computes the total cost of purchase
//Make sure to use input validation that the number of units is greater        than 0
#include <iostream>
using namespace std;

int main ()
{
    double discount, discountTotal, units, total;
    double package = 99;

    cout << "What is the number of units sold? ";
    cin >> units;
    if(units <=0){
        cout << "Units must be greater than 0" << endl;
    }
    if(units > 0 && units < 10)
        discount = .00;
    else if(units >=10 && units <= 19)
        discount = .20;
    else if(units >=20 && units <= 49)
        discount = .30;
    else if(units >=50 && units <= 99)
        discount = .40;
    else if(units >=100, .50)
        discount = .50;

    discountTotal = package * discount;
    total = package - discountTotal;
    cout << "Your total is: " << total << endl;

    return 0;
}

//编写一个程序，询问售出的单位数量并计算购买的总成本
//确保使用输入验证，使单位数大于0
#包括
使用名称空间std；
int main（）
{
双重折扣，折扣总额，单位，总额；
双包装=99；
cout>单位；
如果（单位如果输入不正确，您可以
立即返回
：

if(units <=0){
    cout << "Units must be greater than 0" << endl;        
    return -1; // if the input 0 or negative, the program will end here
}

if（unitsMmm…我认为这样更好：

#include <iostream>
using namespace std;

int main ()
{

    double discount, discountTotal, units, total;
    double package = 99;

    cout << "What is the number of units sold? ";
    cin >> units;

    if(units <=0)
    {
        cout << "Units must be greater than 0" << endl;
    }
    else
    {
        if(units > 0 && units < 10)
            discount = .00;
        else if(units >=10 && units <= 19)
            discount = .20;
        else if(units >=20 && units <= 49)
            discount = .30;
        else if(units >=50 && units <= 99)
            discount = .40;
        else if(units >=100, .50)
            discount = .50;

        discountTotal = package * discount;
        total = package - discountTotal;
        cout << "Your total is: " << total << endl;
    }
    return 0;
}

#包括
使用名称空间std；
int main（）
{
双重折扣，折扣总额，单位，总额；
双包装=99；
cout>单位；
如果（单位）“…但如果值为0，我不会尝试运行它。`“不，你不会，没有条件阻止运行计算并输出总数。
#include <iostream>
using namespace std;

int main ()
{

    double discount, discountTotal, units, total;
    double package = 99;

    cout << "What is the number of units sold? ";
    cin >> units;

    if(units <=0)
    {
        cout << "Units must be greater than 0" << endl;
    }
    else
    {
        if(units > 0 && units < 10)
            discount = .00;
        else if(units >=10 && units <= 19)
            discount = .20;
        else if(units >=20 && units <= 49)
            discount = .30;
        else if(units >=50 && units <= 99)
            discount = .40;
        else if(units >=100, .50)
            discount = .50;

        discountTotal = package * discount;
        total = package - discountTotal;
        cout << "Your total is: " << total << endl;
    }
    return 0;
}