Question

vb中在label输出100-200之间的全部素数。

Private Sub Command1_Click()
For i = 100 To 200
For k = 2 To i - 1
If i Mod k > 0 Then
Label1.Caption = i
End If
Next k
Next i
End Sub
为什么我输出的是200呢？

Answer 1

你少加了输出和换行了。每次for都要赋值一次，才能显示中间所有的数据。
Private Sub Command1_Click()
For i = 100 To 200
For k = 2 To i - 1
If i Mod k > 0 Then
Label1.Caption = i
print i &shr(13)
End If
Next k
Next i
End Sub

Answer 2

你这样写的话只要i不被2到i-1中的任何一个数整除都会判断为是素数，这样是不对的。如i=200，k=3，200 Mod 3 >0，这样你判断200也是素数。

并且Label1.Caption中只能输出最后一个你的判断的数，也就是200.

追问

那应该怎么写呢？

追答

"听不清啊"回答正确

追问

= =

Answer 3

Private Sub Command1_Click()
Label1.Caption = ""
For i = 100 To 200
For k = 2 To Sqr(i)
j = 0
If i Mod k = 0 Then j = 1: Exit For
Next k
If j = 0 Then Label1.Caption = Label1.Caption & " " & i
Next i
End Sub

Answer 4

Private Sub Command1_Click()
For i = 100 To 200
For k = 2 To Int(Sqr(i))
If i Mod k = 0 Then
Exit For
Else
End If
If k = Int(Sqr(i)) Then Label1.Caption = Label1.Caption + Str(i) + ","
Next k
Next i
End Sub