Question

所以设计问题是：

输入3个数字并显示最大值。继续输入3个数字的集合，直到用户想要退出。找出所有最大数字的平均值。

所以输入数字工作正常但是当我尝试插入SENTINEL值来停止循环时我需要为所有3个数字输入它并且它不能给我一个正确的过去的平均值输入数字。

非常感谢任何帮助，谢谢您的时间！

 #include <iostream>
 using namespace std;

int main()
{

    const int SENTINEL = -1;
    int num1;
    int num2 = 0;
    int num3 = 0;
    int largest;
    int sum;
    int count;
    float average;

    // initialize the count and sum
    count = 0;
    sum = 0;

    while (num1 != SENTINEL)
    {

        // Prompt user for the first number or to quit
        cout << "If you want to quit enter " << SENTINEL << " to stop\n " << endl;
        cout << "Enter first number  ";
        cin >> num1;

        // Prompt the user for the second number
        cout << "please enter second number                  ";
        cin >> num2;

        // Prompt the user for a third number
        cout << "please enter the third number               ";
        cin >> num3;

        // Compare numbers 1 and 2 for the largest number
        if (num1 > num2)
        {
            largest = num1;
        }
        else
        {
            largest = num2;
        }

        // Compare largest to last number input
        if (num3 > largest)
        {
            largest = num3;
        }

        // Display the largest number
        cout << "largest number is: " << largest << endl;

        // Increment the count
        count++;

    }



    if (count > 0)
    {
        average = sum / count;
        cout << "Average of the numbers is " << average;
    }

    return 0;
}

Answer 1

使用break;指令是可能的，但通常被认为是不优雅且难以维护。

原因是你打破了代码的流程，你的程序的读者（可能不是你在大程序中或者如果你共享它）期望循环的代码继续到它的结尾。如果你的函数有一个或多个break;指令，可能很难理解函数的意图，因为你必须记住循环已经结束的情况。

解决问题的基本原则是在获取num1的值之后，在正确的位置开始循环。然后你的循环也必须以它结束。这样，您将始终在用户键入num1后立即检查退出条件。

// initialize the count and sum
count = 0;
sum = 0;

// Prompt user for the first number or to quit
cout << "If you want to quit enter " << SENTINEL << " to stop\n " << endl;
cout << "Enter first number  ";
cin >> num1;

while (num1 != SENTINEL)
{

    // Prompt the user for the second number
    cout << "please enter second number                  ";
    cin >> num2;

    // Prompt the user for a third number
    cout << "please enter the third number               ";
    cin >> num3;

    // Compare numbers 1 and 2 for the largest number
    if (num1 > num2)
    {
        largest = num1;
    }
    else
    {
        largest = num2;
    }

    // Compare largest to last number input
    if (num3 > largest)
    {
        largest = num3;
    }

    // Display the largest number
    cout << "largest number is: " << largest << endl;

    // Increment the count
    count++;

    // Prompt user for the first number or to quit
    cout << "If you want to quit enter " << SENTINEL << " to stop\n " << endl;
    cout << "Enter first number  ";
    cin >> num1;
}

if (count > 0)
{
    average = sum / count;
    cout << "Average of the numbers is " << average;
}

return 0;

注意：我没有在这里解决代码错误，如注释中所述（变量未声明，总和未更新等）。

Answer 2

输入num1后立即有条理地断开循环。

cin >> num1;
if (SENTINEL == num1)
{
  break;
}

Answer 3

在

cin >> num1;

你可以查看它的SENTIEL号码是否从循环中断：

if (num1 == SENTIEL)
    break

这样它就不会执行另一个cin了。

在c ++中查找用户输入的最大数字的平均值

3 个答案: