Question

编码新手。我上周有一个项目要求用户输入4个等级，然后计算所有4个等级的平均值，最低等级的平均值下降（已经转为btw）。要求是For Next循环和Do While循环来计算平均值。我使用For Next循环来获得4个等级的总和，然后计算平均值。

    Declare variables, constant, and array
        Const intMAX_SUBSCRIPT As Integer = 3 
        Dim intGrades(intMAX_SUBSCRIPT) As Integer 
        Dim intTotal As Integer = 0     'holds the total of grades
        Dim dblAverage As Double        'holds the average of all 4 grades
        Dim intCount As Integer         'loop counter
        Dim intLowest As Integer        'holds the lowest score

        'assign grades to array slots
        intGrades(0) = CInt(txtGrade1.Text)
        intGrades(1) = CInt(txtGrade2.Text)
        intGrades(2) = CInt(txtGrade3.Text)
        intGrades(3) = CInt(txtGrade4.Text)

        'Loop to calculate average in grades array
        'get total of all grades
        For intCount = 0 To (intGrades.Length - 1)
            intTotal += intGrades(intCount)

        Next
        'use floating-point div to find average
        dblAverage = intTotal / intGrades.Length

这应该有效。然后我使用以下内容找到最低等级：

        intLowest = intGrades(0)

        'Search for the lowest grade in the array
        For intCount = 1 To (intGrades.Length - 1)
            If intGrades(intCount) < intLowest Then
                intLowest = intGrades(intCount)
            End If
        Next

这太有效了。现在我遇到的问题是：得到一个Do While计算新的平均值，得分最低。这是我需要帮助的地方：

        Dim intNewTotal As Integer = 0  'holds the new total of the 3 highest grades
        Dim dblNewAverage As Double 'holds the new average with the lowest score dropped
        Dim intNewCount As Integer = 0 'loop counter 

        Do While intNewTotal <= (intTotal - intLowest)
            intNewTotal = intNewTotal + intGrades.Length - 1
            intNewCount += 1
        Loop

        dblNewAverage = intNewTotal / 3

数学很接近，但并不完全。对于100,100,80和100的成绩，我得到以下结果：所有4的平均值= 95，平均得分最低= 101.新的平均值总是比它应该高一个。我该怎么做才能解决这个问题？我真的很想明白，如果它再次发生，我可以解决这个问题。谢谢！

Answer 1

问题在于这行代码：

intNewTotal = intNewTotal + intGrades.Length - 1

您可以添加intGrades数组的长度，而不是添加成绩值，直到达到Do while条件：intNewTotal <= (intTotal - intLowest)

我理解你的问题是出于学术目的，所以如果你真的需要使用Do While循环计算平均值，我会用那种方式（未经测试）：

Dim index As Int = 0
Do While index <= intMAX_SUBSCRIPT  

  If (intGrades(index) <= intLowest) Then
    intNewTotal += intGrades(index)
    intNewCount += 1    
  End if

  index += 1

Loop

dblNewAverage = intNewTotal / intNewCount

修改

降低最低等级可能会以不同的方式解释。如果您具有值80,80,100,110，则可能只想删除80个值中的一个或两个值。我上面的代码正在删除它们。如果您只想删除其中一个，那么您应该将起始索引设置为1以跳过第一个项目并删除if条件：

Dim index As Int = 1 Do While index <= intMAX_SUBSCRIPT intNewTotal += intGrades(index) index += 1 Loop dblNewAverage = intNewTotal / (intGrades.Length - 1)

Answer 2

这可能是家庭作业，在这种情况下，你无论如何也不会理解这一点。但是，如果您真的想要了解专业人士如何做到这一点，那么代码看起来会更像这样：

Dim Grades As New List(Of Integer) From {CInt(txtGrade1.Text), CInt(txtGrade2.Text), CInt(txtGrade3.Text), CInt(txtGrade4.Text)} 

Dim Total As Integer = Grades.Sum()
Dim Average As Double = Grades.Average()       'holds the average of all 4 grades
Dim Lowest As Integer = Grades.Min()      'holds the lowest score
Dim NewAverage As Double = CDbl(Total - Lowest) / (Grades.Count - 1)

并在您的变量名称上删除愚蠢的类型前缀。在Option Strict是默认值之前，它们曾经很受欢迎并且有意义，但现在甚至微软自己的风格指南都建议不要使用它们。

Answer 3

Dim j As New List(Of Int32)
    Dim sum As Int32 = 0
    For i = 1 To 4 '4 number of textboxes
        j.Add(CType(Controls.Item("txtGrade" + i.ToString), TextBox).Text)
        sum += Val(CType(Controls.Item("txtGrade" + i.ToString), TextBox).Text)
    Next
    j.Sort()
    Dim intLowest As Int32 = j(0)
    Dim avg As Int32 = sum / j.Count

需要VB Do ... while循环计算平均值

3 个答案: