c++ - 平均值计算不正确

Question

我设计了一个小程序来计算一组学生的平均考试成绩，但是，对于我来说，无法弄清楚为什么平均数计算不正确。这是怎么回事？

输出:

Enter number of students in class (max 50): 3 Enter total number of tests (max 10): 3 Enter student 1's test scores: 100 100 100 Enter student 2's test scores: 100 97 75 Enter student 3's test scores: 56 45 67 (lldb) (lldb) (lldb)

The average score for student 1 is 33.3333. // As you see here it should be 100 since all 3 scores were 100. (lldb)

代码:

const int MAX_STUDENTS = 50;
const int MAX_TESTS = 10;

int main()
{
    char studentName[50];
    int totalStudents = 0;
    int totalTests = 0;
    double totalScore = 0;
    double score[MAX_STUDENTS][MAX_TESTS];
    double averages[MAX_STUDENTS];

    std::cout << "Enter number of students in class (max " << MAX_STUDENTS << "): ";
    std::cin >> totalStudents;
    std::cout << "Enter total number of tests (max " << MAX_TESTS << "): ";
    std::cin >> totalTests;
    for (int student = 0; student < totalStudents; student++) {
        std::cout << "Enter student " << (student + 1) << "'s test scores: " << endl;
        for (int test = 0; test < totalTests; test++) {
            std::cin >> score[student][test];
        }
    }

    for (int student = 0; student < totalStudents; student++) {
        for (int test = 0; test < totalTests; test++) {
            totalScore = NULL;
            totalScore += score[student][test];
        }
        averages[student] = totalScore / totalTests;
        std::cout << endl;
        std::cout << "The average score for student " << student + 1 << " is " << averages[student] << "." << endl;
    }

    return 0;
}

Answer 1

改变

    for (int test = 0; test < totalTests; test++) {
        totalScore = NULL;
        totalScore += score[student][test];
    }

到

    totalScore = 0;
    for (int test = 0; test < totalTests; test++) {
        totalScore += score[student][test];
    }

否则，您将在每次添加之前重置 totalScore。