VB学习第十二周输出显示n以内的素数

'(3)输出显示n以内的素数1
Public Class Form1
    Private Sub TextBox1_KeyPress(ByVal sender As Object,ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        Dim i,n,m As Integer,Tag As Boolean
        Dim x() = {0}
        If Asc(e.KeyChar) = 13 Then
            If Not IsNumeric(TextBox1.Text) Then
                TextBox1.Text = ""
                TextBox1.Focus()
            Else
                m = Val(TextBox1.Text)
                For n = 3 To m
                    Tag = True
                    For i = 2 To n - 1
                        If (n Mod i) = 0 Then Tag = False
                    Next
                    If Tag Then
                        If x(0) = 0 Then
                            x(0) = n
                        Else
                            ReDim Preserve x(UBound(x) + 1)
                            x(UBound(x)) = n
                        End If
                    End If
                Next
            End If
            Label3.Text = ""
            If x(0) = 0 Then
                Label3.Text = Str(m) & "以内没有素数"
            Else
                For i = 0 To UBound(x)
                    Label3.Text &= Space(5 - Len(Str(x(i)))) & Str(x(i))
                    If ((i + 1) Mod 5 = 0) Then Label3.Text &= vbCrLf
                Next
            End If
        End If
    End Sub
End Class
'(4)输出显示n以内的素数2
Public Class Form1
    Private Sub TextBox1_KeyPress(ByVal sender As Object,Tag As Boolean
        Dim x() = {0}
        If Asc(e.KeyChar) = 13 Then
            If Not IsNumeric(TextBox1.Text) Then
                TextBox1.Text = ""
                TextBox1.Focus()
            Else
                m = Val(TextBox1.Text)
                For n = 3 To m
                    Tag = True
                    For i = 2 To n - 1
                        If (n Mod i) = 0 Then Tag = False
                    Next
                    If Tag Then
                        If x(0) = 0 Then
                            x(0) = n
                        Else
                            ReDim Preserve x(UBound(x) + 1)
                            x(UBound(x)) = n
                        End If
                    End If
                Next
            End If
            ListBox1.Items.Clear()
            For i = 0 To UBound(x)
                ListBox1.Items.Add(x(i))
            Next
        End If
    End Sub
End Class

（编辑：李大同）

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