用VB编出由1到100里有多少个素数

Question

要求用两种以上的方法

Answer 1

Private Function sushu(ByVal n As Long) As Boolean
Dim i As Long
For i = 2 To n - 1
If (n Mod i) = 0 Then Exit For
Next i
If i = n Then sushu = True
End Function

Private Sub Form_Click()
Dim a As String
For i = 1 To 100
If sushu(i) = True Then
a = a & i & " , "
Else
End If
Next
a = a & "以上是1~100 之间素数的集合"
Print a
End Sub

Private Sub Form_Load()
Me.Move 0, 0, Screen.Width, Screen.Height
End Sub

参考资料：最恨VB是一个最爱VB的人 ^^

Answer 2

如果一个数a不能被2到a/2的数整除，那么就是素数，或者，如果不能被2到sqr(a)的数整除，也是素数。
所以，判断素数的过程可以编写为：
(1)
Private Function isprime (n As integer) As Boolean
Dim i As integer
isprime = false
For i = 2 To n/2
If n Mod i = 0 Then Exit function
Next i
isprime = True
End Function

(2)
Private Function isprime (n As integer) As Boolean
Dim i As integer
isprime = false
For i = 2 To sqr(n)
If n Mod i = 0 Then Exit function
Next i
isprime = True
End Function

主程序可以编写为：
Private Sub Form_Click()
Dim i As integer, num as integer
For i = 1 To 100
If isprime(i) Then
print i;
num = num + 1
if num mod 5 = 0 then print
End If
Next i
print
Print "从1到100共有" & num & "个素数"
End Sub