怎样用VB程序求100——1000的素数

添加一个窗体，三个textbox控件、两个LABEL控件和一个commandbutton控件然后添加如下代码：Private Sub Command1_Click()
   If Not IsNumeric(Text2.Text) Or Not IsNumeric(Text2.Text) Then MsgBox "请输入正确的起始与结束数！": Exit Sub
   If CInt(Text2.Text) >= CInt(Text3.Text) Or Text2.Text < 1 Or Text3.Text < 1 Then MsgBox "您输入的数字不符合要求，请重新输入……": Exit Sub
   Dim i As Integer, n As Integer, percent
   n = 0
   Text1.Text = ""
   Text1.Text = Text2.Text & " 到 " & Text3.Text & " 之间的素数有：" & vbCrLf
   For x = Text2.Text To Text3.Text
      For i = 2 To x - 1
         If (x Mod i) = 0 Then GoTo g_next
      Next
      If n <= 4 Then
         Text1.Text = Text1.Text & x & Chr(9)
         n = n + 1
      Else
         Text1.Text = Text1.Text & x & vbCrLf
         n = 0
      End If
      Text1.SelStart = Len(Text1.Text)
      Text1.Refresh
g_next:
   Next
End Sub

'筛法：
Dim isPrime(1 To 1000) As Boolean
Dim i, j As Integer, s As Single'筛除所有偶数
For i = 3 To 1000 Step 2
    isPrime(i) = True
Next iFor i = 3 To 1000 Step 2
    If isPrime(i) Then
        '素数验证
        For j = 3 To i \ 2 Step 2
            s = i
            s = s / j
            If s = i \ j And s > 1 Then
                isPrime(i) = False
                Exit For
            End If
        Next j
        '筛除所有倍数
        If isPrime(i) Then
            For j = i * 3 To 1000 Step 2 * i
                isPrime(j) = False
            Next j
        End If
    End If
Next iFor i = 100 To 1000
    If isPrime(i) Then Debug.Print i
Next i

...........
    For x = Text2.Text To Text3.Text
      For i = 2 To x\2
         If (x Mod i) = 0 Then GoTo g_next
      Next
.............
     这样算法效率更高！

效率最高的应该是: For i = 2 To sqr(x)只需要判断到x能否被x的平方根整除就够了。

给你一个比较有趣的算法——枪毙算法。
原理是这样的：
有x个鬼子，你从第2号开始处理。如果你遇到第n号鬼子是活的，从n*2号开始逢n的倍数毙一个。如此循环一直枪毙到n=SQR(x)个，这个时候就没有可毙的了。接着开始收尸，遇到活的鬼子把它编号记下，这些号码就是x以内所有素数。
这个算法优点是速度比较快，缺点则是需要大量的内存空间。你想求x以内的素数，则需要x个元素。该算法如果用链表改进的话，速度更快。Function KillNums(ByVal pBound As Integer) As Long()
  Dim tOutNums() As Long     '幸存素数
  Dim tAllNums() As Boolean  '刑场数组
  ReDim tAllNums(pBound)
  Dim tStepIndex As Long
  Dim tNumIndex As Long
  Dim tOutIndex As Long
  Dim tOutLength As Long
  '枪毙过程
  For tNumIndex = 2 To Sqr(pBound)
    If Not tAllNums(tNumIndex) Then '如果第tNumIndex个是活的
      For tStepIndex = (tNumIndex * 2) To pBound Step tNumIndex
        '从tNumIndex * 2开始，遇到tNumIndex的倍数枪毙一个。
        tAllNums(tStepIndex) = True
      Next
    End If
  Next
  '收尸过程
  For tNumIndex = 2 To pBound
    If Not tAllNums(tNumIndex) Then '如果是活的记下号码。
      ReDim Preserve tOutNums(tOutLength)
      tOutNums(tOutLength) = tNumIndex
      tOutLength = tOutLength + 1
    End If
  Next
  KillNums = tOutNums()
End FunctionPrivate Sub Command1_Click()
  Dim tLongs() As Long
  tLongs() = KillNums(1000)
  Dim tIndex As Long
  For tIndex = 0 To UBound(tLongs())
    Text1.Text = Text1.Text & tLongs(tIndex) & vbCrLf
  Next
End Sub

呵呵，下面我发一个最有效率的算法：：：：：
        'sheng cheng zhishu
        Dim z(100) As Integer
        z(1) = 2
        z(2) = 3
        z(3) = 5
        z(4) = 7
        Dim i As Integer = 5
        Dim mun As Integer = 11
        Do While i < 101
            If mun Mod 2 > 0 And mun Mod 3 > 0 And mun Mod 5 > 0 And mun Mod 7 > 0 Then
                z(i) = mun
                i += 1
            End If
            mun += 1
        Loop

shenyuflying请注意你的结果，速度是快了，但差不多有一半的非素数在里面哦！我们编程首先是要能得出正确的结果，在正确结果的前提下提高算法效率才是正确的！！！！！

只判断素数因数即可：Sub findprimes()
Dim i As Long, j As Byte, n As Long, beprime As Boolean, s() As String, p
p = Array(3, 5, 7, 11, 13, 17, 19, 23, 29, 31)
For i = 101 To 1000 Step 2
beprime = True
For j = 0 To 9
If i Mod p(j) = 0 Then beprime = False: Exit For
If p(j) > Sqr(i) Then Exit For
Next
If beprime = True Then
n = n + 1
ReDim Preserve s(1 To n)
s(n) = i
End If
Next
MsgBox Join(s, ","), , "100-1000中有 " & n & " 个素数"
End Sub

时间效率较高的解法之一:Option ExplicitPrivate Sub Form_Load()
    Const Min = 100
    Const Max = 1000
    Dim A(2 To Max) As Boolean
    Dim i As Integer, j As Integer
    For i = 2 To Max
        If Not A(i) Then
            For j = 2 To Max \ i
                A(i * j) = True
            Next j
        End If
    Next i
    For i = Min To Max
        If Not A(i) Then Debug.Print i;
    Next i
    End
End Sub

Option Explicit
Private Declare Function GetTickCount Lib "kernel32.dll" () As LongPrivate Sub Command1_Click()
Const Min = 100
Const Max = 1000
Dim i As Integer, j As Integer, k As Integer, t As Long
t = GetTickCount
For k = 1 To 1000
    For i = Min To Max
            For j = 2 To Sqr(i)
                If (i Mod j) = 0 Then GoTo l1
            Next j
            'Debug.Print i;
l1:
    Next i
Next k
MsgBox "      Time:" & GetTickCount - t & vbCrLfEnd SubPrivate Sub Command2_Click()
Const Min = 100
Const Max = 1000
Dim A(2 To Max) As Boolean
Dim i As Integer, j As Integer, k As Integer, t As Long
t = GetTickCount
For k = 1 To 1000

    For i = 2 To Max
        If Not A(i) Then
            For j = 2 To Max \ i
                A(i * j) = True
            Next j
        End If
    Next i
    For i = Min To Max
        'If Not A(i) Then Debug.Print i;
    Next i
Next kMsgBox "      Time:" & GetTickCount - t & vbCrLfEnd Subjadeluo(秀峰) 方法比传统的方法还是很有优势的

调试易

怎样用VB程序求100——1000的素数

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