Question

我应该允许用户输入非负数，一旦输入了负数，该功能应显示进行中的非负数的平均值。

我正在使用XCode进行C ++工作。

int Question6(){
    double nums;
    double totalnums = 0;
    int count = 0;

    cout << "Please enter the numbers that you like to be average that are non-negative:";
    cin >> nums;

    while (nums > 0){
        cout << "Please enter the numbers that you like to be average that are non-negative:";
        cin >> nums;
        totalnums += nums;
        count += 1;

        if (nums < 0){

            cout << "You have enterd a negative number so your average is:" << (totalnums/ count) << endl;

        }

    }

    return 0;
}

我获得了成功的构建，但是它总是给我一个包含负数的平均值。有办法阻止这种情况发生吗？

Answer 1

问题在这里：

int menu(std::vector <std::string> options) //menu creation
{
int input;             //user selection
bool check = false;    //check for valid input
.
.
.
while(!check)
{
    std::cin >> input;

    if(std::cin.fail() || input <= 0 || input > static_cast<int>(options.size()))
    {
        std::cin.clear();
        std::cin.ignore();
        std::cout << wrongInput << std::endl;
    }
    else
    {
        check = true;       //change flag for valid input
    }
}
return input;
}

问题是while (nums > 0) { cout << "Please enter the numbers that you like to be average that are non-negative:"; cin >> nums; totalnums += nums; count += 1; if (nums < 0) { cout << "You have enterd a negative number so your average is:" << (totalnums/ count) << endl; } }循环中的if指令。如果输入负数，它将被添加到while指令中，因为它是totalnums+=nums之后的下一条指令。之后，cin条件变为while，程序退出循环。

要解决您的错误，请检查false 之前，然后进入nums<0循环。

Answer 2

更干净的解决方案-具有错误检查 的-在有效输入时循环播放，然后根据输入的符号决定要执行的操作：

while (std::cin >> number)
{
  if (number >= 0)
  {
     // update values needed for average calculation
  }
  else
  {
     // calculate average, display
     break; // exit the while loop
  }
}
// Optionally: Check if loop exited due to read error or negative number
if (std::cin)
{
  // read a negative value
}
else
{
  // IO error (such as eof, no more numbers)
}

将非负数取平均值的函数

2 个答案: