Question

我的程序存在一些问题，该程序在2D字符串数组中保存学生姓名和成绩。基本上，我有一个第二个（1D）阵列，可以保持每个学生的平均成绩。

到目前为止

代码：

class Program
{
    static void Main(string[] args)
    {
        // Create a 2D array for names, and their grades, and an array for average grades
        string[,] studentGrades = new string[5, 8];
        int[] average = new int[studentGrades.GetLength(0)];

        // Set student names/grades manually
        studentGrades[0, 0] = "Steve";
        studentGrades[0, 1] = "69";
        studentGrades[0, 2] = "80";
        studentGrades[0, 3] = "66";
        studentGrades[0, 4] = "75";
        studentGrades[0, 5] = "90";
        studentGrades[0, 6] = "69";
        studentGrades[0, 7] = "98";

        studentGrades[1, 0] = "Bob";
        studentGrades[1, 1] = "73";
        studentGrades[1, 2] = "67";
        studentGrades[1, 3] = "65";
        studentGrades[1, 4] = "91";
        studentGrades[1, 5] = "48";
        studentGrades[1, 6] = "33";
        studentGrades[1, 7] = "94";

        studentGrades[2, 0] = "Lewis";
        studentGrades[2, 1] = "67";
        studentGrades[2, 2] = "80";
        studentGrades[2, 3] = "66";
        studentGrades[2, 4] = "75";
        studentGrades[2, 5] = "90";
        studentGrades[2, 6] = "69";
        studentGrades[2, 7] = "63";

        studentGrades[3, 0] = "Sara";
        studentGrades[3, 1] = "55";
        studentGrades[3, 2] = "58";
        studentGrades[3, 3] = "63";
        studentGrades[3, 4] = "70";
        studentGrades[3, 5] = "55";
        studentGrades[3, 6] = "55";
        studentGrades[3, 7] = "76";

        studentGrades[4, 0] = "Xavier";
        studentGrades[4, 1] = "22";
        studentGrades[4, 2] = "27";
        studentGrades[4, 3] = "25";
        studentGrades[4, 4] = "19";
        studentGrades[4, 5] = "42";
        studentGrades[4, 6] = "18";
        studentGrades[4, 7] = "32";

        // Loop the array dimensions and output/format output the names/grades
        for (int name = 0; name < studentGrades.GetLength(0); name++)
        {
            for (int grade = 0; grade < studentGrades.GetLength(1); grade++)
            {
                Console.WriteLine(studentGrades[name, grade]);
            }
            Console.WriteLine("");
        }

        for (int i = 0; i < studentGrades.GetLength(0); i++)
        {
            for (int j = 0; j < studentGrades.GetLength(1); j++)
            {
                average[j] += int.Parse(studentGrades[i, j]);
            }
        }

    }
}

关于输入字符串没有设置平均值的正确格式，我得到了一个未处理的异常。

感谢所有帮助！

更新

我已经回顾了目前为止的代码解决方案，而且我仍然遇到让平均成绩按预期工作的问题。我有5个学生，7个年级。我希望程序输出每列人员的平均成绩。

代码：

static void Main(string[] args)
    {
        // Create a 2D array for names, and their grades, and an array for average grades
        string[,] studentGrades = new string[5, 8];
        int[] average = new int[studentGrades.GetLength(1)];

        // Set student names/grades manually
        //As done above, excluded for brevity reasons


        // Loop the array dimensions and output/format output the names/grades
        for (int grade = 0; grade < studentGrades.GetLength(1); grade++)
        {
            for (int name = 0; name < studentGrades.GetLength(0); name++)
            {
                // Composite formatting is used to align names/grades in grid -- specifically the alignment component.
                // Making the value higher (more neg) will increase spacing between elements
                // Positive number would right align elements instead
                Console.Write("{0, -15}", studentGrades[name, grade]);
            }
            // Moves each printed grade to a new line
            Console.WriteLine("");
        }

        for (int i = 0; i < studentGrades.GetLength(0); i++)
        {
            for (int j = 1; j < studentGrades.GetLength(1); j++)
            {
                average[j] += int.Parse(studentGrades[i, j]);
            }

            average[i] /= studentGrades.GetLength(1) - 1;
        }

        for (int i = 0; i <= average.GetLength(0) - 1; i++)
        {
            Console.Write("{0, -15}", i);
        }
        Console.WriteLine("");


    }

更新2

似乎平均数组没有正确填充。如果我删除平均分区，它似乎只打印出1,2,3,4,5,6,7。此外，如果我将平均值的长度更改为5 - 或者名称数量的长度，因为只有5个值，它会中断。这可能是因为它试图将7个项目添加到5个项目数组中。

Answer 1

每个int元素都不是整数，因此您无法将其解析为for (int i = 0; i < studentGrades.GetLength(0); i++) { for (int j = 1; j < studentGrades.GetLength(1); j++) { average[j] += int.Parse(studentGrades[i, j]); } }

略过第一个元素

Numeric

Answer 2

您尝试在平均值中包含名称字符串（在0索引上）。例如导致异常的for (int j = 1; j < studentGrades.GetLength(1); j++)，只需跳过每个列上的第一个元素。

{{1}}

Answer 3

您必须更改此部分代码：

// Store the average as a double array, otherwise you can't have averages with decimal values.
double[] average = new double[studentGrades.GetLength(0)];

for (int i = 0; i < studentGrades.GetLength(0); i++)
{
    // Start from j = 1, as j = 0 would get a name instead of a grade.
    for (int j = 1; j < studentGrades.GetLength(1); j++)
    {
        // Here use average[i] instead of average[j], because you want
        // the average grade for each student.
        average[i] += int.Parse(studentGrades[i, j]);
    }

    // Finish calculating the average.
    // GetLength(0) - 1 because the first item is a name, not a grade.
    average[i] /= studentGrades.GetLength(1) - 1;
}

for (int i = 0; i <= average.GetLength(0) - 1; i++)
{
    // Show at most 2 decimal digits.
    Console.Write("{0, -15:#.##}", average[i]);
}

Answer 4

正如其他人正确指出的那样，您需要在以下行中将0更改为1：

for (int j = 1; j < studentGrades.GetLength(1); j++)

否则，您将尝试将名称解析为整数。

此外，您需要将循环内的平均索引更改为i而不是j。

average[i] += int.Parse(studentGrades[i, j]);

您将要使用的另一个问题是您使用整数数学 - 所以当您执行7 / 2之类的操作时，您会得到3而不是3.5的答案

如果我是你，而你不想改变你的数据结构，我会这样做：

var results =
    studentGrades
        .Cast<string>()
        .Select((x, n) => new { x, n })
        .GroupBy(xn =>  xn.n / studentGrades.GetLength(1), xn => xn.x)
        .Select(xs => new
        {
            student = xs.First(),
            average = xs.Skip(1).Select(x => int.Parse(x)).Average(),
        })
        .ToArray();

这让我：

或者，我建议您将数据结构更改为：

var studentGrades = new []
{
    new { student = "Steve", grades = new [] { 69, 80, 66, 75, 90, 69, 98, } },
    new { student = "Bob", grades = new [] { 73, 67, 65, 91, 48, 33, 94, } },
    new { student = "Lewis", grades = new [] { 67, 80, 66, 75, 90, 69, 63, } },
    new { student = "Sara", grades = new [] { 55, 58, 63, 70, 55, 55, 76, } },
    new { student = "Xavier", grades = new [] { 22, 27, 25, 19, 42, 18, 32, } },
};

然后这应该适合你：

var results =
    studentGrades
        .Select(sg => new
        {
            sg.student,
            average = sg.grades.Average(),
        })
        .ToArray();

2D字符串数组中{int}值的平均数组

更新

更新2

4 个答案: