Question

需要一些帮助，如何找到儿童使用计数器，累加器和结束哨兵销售的饼干的平均数量（基本编程hwk，yay！）。我有一个问题，弄清楚为什么普通的盒子打印出错误的数字。

例如：

Program result prints out -5 averageBoxes when that's clearly not right...

{
    int numBoxes,
        // Number of boxes of cookies sold by one child
        totalBoxes = 0,   // Accumulates total boxes sold by the entire troop
        numSeller = 1;    // Counts the number of children selling cookies

    double averageBoxes; // Average number of boxes sold per child

                         // Write code to initialize the totalBoxes accumulator to O and
                         // The numSeller counter to 1.

    cout << "**** Cookie Sales Information ****\n";

    // Get the first input
    cout << "Enter number of boxes of cookies sold by seller " << numSeller
        << " (or -1 to quit): ";
    cin >> numBoxes;

    // Write code to start a while loop that loops while numBoxes
    // is not equal to -1, the sentinel value.

    while(numBoxes != -1)
    {
        // Write code to add numBoxes to the totalBoxes accumlator.
        // Write code to add 1 to the numSeller counter.

        totalBoxes += numBoxes;
        numSeller++;

        // Write code to prompt for and input the number of boxes
        // sold by the next seller.

        cout << "Enter the number of boxes sold by girl scout # " << numSeller << ": ";
        cin >> numBoxes;
    }

    // When the loop is exited, the value stored in the numSeller counter
    // will be one more than the actual number of sellers. So write code
    // to adjust it to the actual number of sellers.

    numSeller = numSeller - 1;

    if(numSeller == 0)       // If true, -1 was the very first entry
        cout << "\nNo boxes were sold.\n";
    else
    {  // Write code to assign averageBoxes the computed average number
       // of boxes sold per seller.
       // Write code to print out the number of sellers and average number
       // of boxes sold per seller.

        averageBoxes += numSeller / numBoxes;

        cout << "The average number of boxes sold by the " << numSeller << " sellers was " << averageBoxes << endl;
    }

    return 0;
}

它可能是一个简单的解决方案，但任何帮助都将不胜感激，谢谢！

Answer 1

您离开double averageBoxes;未初始化（它有一个不确定的值，而+=只会产生另一个不确定的值。）
您应该将其中一个操作数（或两者）强制转换为浮点类型，因此numSeller / numBoxes的结果是浮点类型：
```
averageBoxes += numSeller / static_cast<double>(numBoxes);
```

修改

好的，你在上面的表达式中使用了错误的变量（由于它们的名字很容易这样做）。它应该是：

averageBoxes += totalBoxes / static_cast<double>(numSeller);

也许只是不要在程序的顶部声明你的变量（不给它们一个值）。在你第一次使用它们时声明它们：

// += wasn't needed in any case double averageBoxes = totalBoxes / static_cast<double>(numSeller);

（C ++）使用while循环计算平均数

1 个答案: