c++ - 程序调试

Question

程序输出应如下所示：

Enter an even number: 23
The number is not a positive even number.
Enter an even number: -6
The number is not a positive even number.
Enter an even number: 4

20 20.25 20.50 20.75 21
The sum is 102.5

程序运行不正常。奇数/偶数被识别，但增加变量的循环（20 + 1 /（输入的偶数））不能正常工作。

#include <iostream>

int main(int argc, char *argv[])
{

    float val, sum, incr;
    int num;

    cout << "Enter an even number: ";
    cin >> num;

    if (num % 2 != 0)
        cout << "The number " << num << " is not a positive even number." << endl;
    else
        cout << num << " is even!" << endl << endl;


    incr = 1 / num;

    for (val = 20.0F; val <= 21.0; val += incr)
    {
        cout << val;
        sum += val;
    }

    cout << "The sum is " << sum << endl;

    return 0;

}

Answer 1

如果你将一个整数除以另一个整数 1，num结果是一个整数，正如克里斯所说的 0。

你应该做：

incr = 1.0F / (float)num;

为了退出错误的引入值，您应该从 main 返回

#include <iostream>

int main() {
    float val, sum, incr;
    int num; 

    cout << "Enter an even number: ";
    cin >> num;
    if (num < 0 || num % 2 != 0){
        cout << "The number " << num << " is not a positive even number." << endl;
        return -1;
    }
    else {
        cout << num << " is even!" << endl << endl;
    }

    incr = 1.0 / num;
    for (val = 20.0F; val <= 21.0; val += incr) {
        cout << val << " ";
        sum += val;
    }
    cout << "The sum is " << sum << endl;
    return 0;
}