sub子過程與函數(shù)調(diào)用素數(shù)課件

1、執(zhí)教者：宋遠(yuǎn)良 素數(shù) -算法及算法實現(xiàn) 所謂素數(shù)是指在一個大于1的自然數(shù)中,除了1和此整數(shù)自身外,不法被其他自然數(shù)整除的數(shù).概念:算法思想: 根據(jù)素數(shù)只能被1和它本身整除的性質(zhì),我們可以使用循環(huán)依次判斷2到n-1(sqr(n)之間有沒有被它整除的數(shù),一旦有退出循環(huán),退出循環(huán)后通過檢驗循環(huán)變量的值來判斷是不是素數(shù).即當(dāng)循環(huán)正常退出,循環(huán)變量的值等于n時,說明該數(shù)是素數(shù),當(dāng)循環(huán)提前退出,循環(huán)變量的值小于等n-1,該數(shù)不是素數(shù).流程圖:Y開始結(jié)束輸入ni =i +1n mod i=0?Exit Nn1?YNi=2i=n-1?Yi =n?n 是素數(shù)n 不是素數(shù)YN試一試1:程序代碼:n = Val(T

2、ext1.Text)If n 1 Then MsgBox 請正確輸入數(shù)據(jù)Else For i = 2 To n - 1 If n Mod i = 0 Then Exit For Next i If i = n Then MsgBox n & 是素數(shù) Else MsgBox n & 不是素數(shù) End IfEnd If程序代碼:根據(jù)標(biāo)志值flag來判斷是否為素數(shù).Dim flag As Booleanflag = Truen = Val(Text1.Text)If n 1 Then MsgBox 請正確輸入數(shù)據(jù)Else For i = 2 To n - 1 If n Mod i = 0 Then

3、flag = False Next i If flag = True Then MsgBox n & 是素數(shù) Else MsgBox n & 不是素數(shù) End IfEnd If試一試2:找出100至999之間的素數(shù),并在列表 框中以每行10個(columns屬性改為10) 顯示出來.程序代碼:Private Sub Command1_Click() Dim k As Integer For k = 100 To 999 If isprime(k) Then List1.AddItem k End If Next kEnd SubPrivate Function isprime(n As Integer) As Boolean Dim i As Integer isprime = True For i = 2 To n - 1 If n Mod i = 0 Then isprime = False Exit Function End If Next iEnd Function函數(shù)或者是:Private Function isprime(n As Integer) As BooleanDim i As Integer isprime = false For i = 2 To n - 1 If n Mod i = 0 T