c++ - 常数变量乘以用户输入

Question

我一直在尝试创建一个简单的程序，允许我在用户输入成功命中数 totalHits 后显示总分，方法是将该输入乘以常量 POINTS 导致另一个变量； 得分。

我不认为创建这样的程序会有任何问题，但像往常一样，我错了.. 当我运行程序时 score 总是随机的，即使我输入'1'每次都是 totalHits。它可以从 444949349 到 -11189181 不等，仅举几个例子。我不知道我做错了什么，所以如果有人能给我下一步该怎么做的线索那就太好了:)

代码如下:

#include <iostream>
using namespace std;

int main()
{
    const int POINTS = 50;
    int totalHits;
    int score = totalHits * POINTS;

    cout << "Please enter the ammount of successful hits: ";
    cin >> totalHits;
    cout << "You hit " << totalHits << " targets, and your ";
    cout << "score is " << score << " ." << endl;

    cin.ignore(cin.rdbuf()->in_avail() + 2);
    return 0;
}

非常感谢 KerrekSB 和 Paddyd 为我提供了正确的答案。这是带有注释的完成代码:

#include <iostream>
using namespace std;

int main()
{
    const int POINTS = 50;
    int totalHits;

    cout << "Please enter the ammount of successful hits: ";
    cin >> totalHits;
    cout << "You hit " << totalHits << " targets, and your ";
    /*As you can see I moved the line below from the top of the code.
    The problem was I had not properly learned how C++ executes the code.
    The orignal code was written in a way that calculates `score` before
    the user could decide it's value, resulting in a different total score than
    it should have been. In the finished code, the user inputs what
    value `totalHits` is, THEN score is calculated by using that value. */
    int score = totalHits * POINTS;
    cout << "score is " << score << " ." << endl;

    cin.ignore(cin.rdbuf()->in_avail() + 2);
    return 0;
}

Answer 1

int totalHits;
int score = totalHits * POINTS;

您正在乘以一个未初始化的变量 (totalHits)!在进行此计算之前，您需要对 totalHits 应用一个值。

尝试使用这样的代码:

const int POINTS = 50;
int totalHits;
int score;

cout << "Please enter the ammount of successful hits: ";
cin >> totalHits;
cout << "You hit " << totalHits << " targets, and your ";
score = totalHits * POINTS;                   //totalHits has a value here
cout << "score is " << score << " ." << endl;

cin.ignore(cin.rdbuf()->in_avail() + 2);
return 0;