計算機等級考試二級VB常用算法

1、一、字符處理11、算法說明1）加密解密最簡單的加密方法是：將每個字母加一序數(shù)，例如5，這時：t g ”A t F , a t f , Bt” G , ” b”t ” D”，” y ” t ” d ” , ” Z”t ” E”,zt e解密是加密的逆操作。界面如下:代碼如下：Word-WRAP: break-word bgColor=#f3f3f3以下是引用片段：Opti onExplicitPrivate Sub Comma nd1_Click()Dim strln put$, Code$, Record$, c As Stri ng* 1Dim i%,len gth%,iAsc%strI n

2、put = Text1.Textlen gth= Len( Trim(strI nput)Code =For i =1Tolen gthc = mid(strI nput, i, 1)Select Case cCase A To ZiAsc =Asc(c)+ 5If iAsc Asc(Z)The niAsc=iAsc -26Code =Code& Chr(iAsc)Case aToziAsc =Asc(c)+ 5If iAsc Asc(z)The niAsc=iAsc -26Code = Code & Chr(iAsc)Case ElseCode = Code & cEnd SelectNex

3、t iText2.Text = CodeEnd SubPrivate Sub Comma nd3_Click()Text1.Text=Text2.Text=Text3.Text=Text1.SetFocusEnd Sub2)統(tǒng)計問題提出統(tǒng)計字符或者數(shù)字出現(xiàn)的次數(shù)。算法說明以字符統(tǒng)計為例，設基本問題如下：請統(tǒng)計一段文本中英文字母在文本中出現(xiàn)的次數(shù)。(不區(qū)分大小寫)女口： I am a student.得到：A:2 d:1 e:1 1:1 m:1 n:1 s:1 t:2 u:1分析：由于不區(qū)分大小寫，因此可定義一個大小為26(下標：0-25)的數(shù)組，每個元素依次記錄A B、C-Z字母出現(xiàn)的次數(shù)。A

4、(0)存放字母a出現(xiàn)的次數(shù)A(1)存放字母b出現(xiàn)的次數(shù)A(2)存放字母c出現(xiàn)的次數(shù)A(3)存放字母d出現(xiàn)的次數(shù)譬如：aabdc代碼如下：以下是引用片段：Opti on ExplicitPrivateSub Comma nd1_Click()Dimi As In teger,j As In tegerDimzimu(25) As In tegerDimallStrAs Stri ngDimaStrAs Stri ngallStr=UCase(Text1.Text)Fori =1 To Len (Text1.Text)aStr=Mid(allStr,i,1)IfaStr=A And aStr =

5、Z Thenzimu(Asc(aStr) -Asc(A)= zimu(Asc(aStr) -Asc(A)+1End IfNext iFor i =0 To 25If zimu(i) 0 The nj = j + 1Text2.Text = Text2.Text & Chr(i + Asc(A)& :& str(zimu(i) &If j Mod 5= 0 Then Text2.Text = Text2.Text & Chr(13)& Chr(10)End IfNext iEnd Sub解題技巧熟練運用字符處理函數(shù)，對于一些數(shù)論題，譬如逆序數(shù)等也可將數(shù)字通過CStr函數(shù)轉(zhuǎn)換為字符后，利用字符處理

6、函數(shù)來解題。2、實戰(zhàn)練習1)補充代碼(2003秋二(8)下面程序的功能是統(tǒng)計文件中英文字母(不區(qū)分大小寫)出現(xiàn)的個數(shù)。Word-WRAP: break-word bgColor=#f3f3f3以下是引用片段：Option Base 1Private Sub Comma nd1_Click()Dim alpha(26) As In teger, n As In tegerDim i As In teger,s As StringOpe n c:kav2003readme.txtFor In put As #11Do While Not EOF(11)s= (1)s=UCase(s)If s=A

7、And s=ZThe nn= (2)alpha (n)=alpha( n)+1End IfLoopFor i=1 To 26If alpha(i)0 The nList1.Addltem Chr(i+64) &:&CStr(alpha(i)End IfNext iCloseEnd Sub2)補充代碼(2000秋二(6)F面程序的功能是：統(tǒng)計當前盤當前文件夾中的順序文件data.txt中共有多少個單詞,約定連續(xù)出現(xiàn)的字母定義為一個單詞。以下是引用片段：Opti on ExplicitPrivateSub Form_Click()DimChar() As Stri ng,StAs Stri ng,

8、TemAs Stri ngDimIdx As In teger,JsAs Long,Fle nAsLo ngDimF As Boolean,W AsStri ng*1(1)Flen=LOF(10)St=In put(Fle n,#10)Js=1DoWhile Js 以下是引用片段:Private Sub Comma nd1_Click()Dim n%, i%x =1第七天桃子數(shù)Print 第七天桃子數(shù)：1只”For i =6 To 1 Step -1x = (x +1)*2Print 第”& i & ”天桃子數(shù):& x & ”只”Next iEnd Sub窮舉法又稱枚舉法，即將所有可能情況一一

9、測試，判斷是否滿足條件，一般用循環(huán)實現(xiàn)。問題：百元買雞問題。假定小雞每只5角;公雞每只2元；母雞每只3元?，F(xiàn)在有100元，要求買100只雞，編 程列出所有可能的購雞方案。分析：設母雞、公雞、小雞分別 x、y、z只，則有：x+y+z=1003x+2y+0.5z=100程序以下是引用片段:PrivateSubComma nd1_Click()Dim x%,y%,z%For x =:0To100For y =:0To100For z =:0To100If x + y+ z=100 And 3*x+2*y+0.5 *z：=100 ThenPrint x, y, zEnd IfNext zNext yN

10、ext xEnd Sub程序二（優(yōu)化）以下是引用片段:PrivateDim x%,For x =For y =If 3 *Print x,End IfNext yNext xEnd SubSub Comma nd1_Click() y%0 To 330 To 50x +2* y +0.5y, 100- x - y*(100- x-y)=100 Then2）高等數(shù)學 求積分 近似計算積分 代碼如下：s=/ 13(x3+2x+5)dx以下是引用片段:PublicFu nctionf(ByVal x!)被積函數(shù)f = x* (x * x +2)+5End FunctionPublic Fun cti

11、 on trapez(ByVala!, ByVal b!,ByValn%) As Singleb、a分別為積分上下限，n為等分數(shù)Dim sum!,h!,x!h = (b- a) / nsum = (f(a)+ f(b)/2For i = 1 T on- 1x = a + i * h sum = sum + f(x) Next i trapez = sum * h End Function調(diào)用：以下是引用片段：Private Sub Comma nd1_Click()Print trapez(1, 3,30)End Sub數(shù)論綜合題此類題目比較廣泛，必須給以足夠重視。歷年題目有：平方數(shù)、零巧數(shù)、

12、擬互滿數(shù)、回文數(shù)、酉完數(shù)、完數(shù)、幸運數(shù)、逆序數(shù)以 及無暇素數(shù)、超級素數(shù)、因子和等。排序21）補充代碼（2002秋二（10）找出由兩個不同數(shù)字組成的平方數(shù)，并將結(jié)果按圖中的格式顯示在列表框Listl 中。Word-WRAP: break-word bgColor=#f3f3f3Opti on ExplicitPrivateSub Comma nd1_Click()DimI As Long,N As LongForI =11 To300(1)IfVerify(N)The n(2)EndIfNextIEndSubPrivateFunctionVerify(3)DimA(0 To 9)As In te

13、ger,DoWhile N 0(4)N =N 10LoopForI =0 To9Js=Js + A(I)NextI(5)EndFunction以下是引用片段:) As Boolea nI As In teger,Js As In teger1）編程題（2004秋上機試卷08）一個正整數(shù)被稱為奇妙平方數(shù)，如果此數(shù)的平方與它的逆序數(shù)的平方互為逆序數(shù)。例如,12人2=144, 222=441,12與21 互逆，144 與441 互逆,12 就是奇妙平方數(shù)。找出1-300以內(nèi)所有的奇妙平方數(shù)。1算法說明1) 順序查找逐個元素找，如果有，則記錄位置，然后跳出循環(huán)；否則，查找失敗。代碼如下：Word-WR

14、AP: break-word bgColor=#f3f3f3以下是引用片段：Private Sub Search(a(), ByVal Key, Index As In teger)Dim i%For i = LBou nd(a) To UBou nd(a)If a(i) = Key Then 找到，將元素下標保存在index中并結(jié)束查找In dex = iExit SubEnd IfNext iIndex =-1若沒找到，則index值為-1End Sub2) 二分法查找順序查找效率低下，當數(shù)組有序排列時，可以使用二分法查找提高效率。 算法思想：塚嚴圈,comm rr學院代碼如下：以下是引用

15、片段:Private Sub birSearch(a(), ByVai low%, ByVai high%, ByVai Key,in dex%)Dim mid As In tegerIf low highThen 沒有查找到in dexExit=-1SubEndIfmid=(low +high) 2取查找區(qū)間的中點If Key = a(mid)Then 查找到，返回下標in dex=midExitSubElselfKey 以下是引用片段：Opti on ExplicitOptionBase 1PrivateSub Form_click()Dim stu() As String, glass(

16、) As Stri ng, i As In tegerDim n As Integer,name As String, k As IntegerOpe n c:stustu.txtFor In put As #11Do While (1)(2)ReDim Preserve stu(n),glass(n)In put #11,stu( n),glass (n)Loopname = InputBox(輸入欲查找的學生姓名：)Call search( name, stu, k)If k = n The nMsgBox (3)ElseMsgBox 無此人。”End IfClose #11End Sub

17、Private Sub search( nameAs String, stu() As String, k As In teger)Dim i As In tegerFor i =1 To UBou nd(stu)Ifn ame = stu(i) The n(4)End IfNext i(5)End Sub1、算法說明數(shù)組中元素的插入和刪除一般是在已固定序列的數(shù)組中插入或刪除一個元素, 使得插入或刪除操作后的數(shù)組還是有序的?；舅悸罚菏紫纫业讲迦胛恢没蛞獎h除的元素。1）插入J1 以下是引用片段:Private Sub Comma nd1_Click()Dima(10)As In tegerD

18、imi AsIn teger,k As In tegerFori =0 To 9 生成數(shù)組a(i)=i*3+1Printa(i)；NextiPrintPrint插入14Fork =0 To 9 查找插入14在數(shù)組中的位置If 14 以下是引用片段：Opti onExplictPrivate Sub Form_Click()Dim A(10) As In teger,i As In teger,J As In tegerOpe n c:Data4.txt For In put As #12Do (1)J=J+1In put #12,A(J)LoopCall In sert(A)For i=1 T

19、o 10Print A(i);Next iPrintClose #12EndSubPrivateSub In sert(A()AsIn teger)Dimi As In teger,PutpAsIn teger,JAs In tegerDimGetp As In teger,NAsIn teger,TemAs In tegerN=UBou nd(A)/2Putp=1Getp=N+1For i=1 To NTem=A(Getp)For J=Getp To Putp +1 Step -1(2)Next JA(Putp)=Tem Getp=Getp+1 Putp= (3) Next iEnd Sub

20、補充代碼下面程序得功能是將無序數(shù)組中相同得數(shù)只保留一個，其余得刪除，并輸出經(jīng)過刪除后的數(shù)組元素，刪除相同數(shù)是通過將該數(shù)組元素后面的元素在數(shù)組內(nèi)依次前移替換前一個元素 的值實現(xiàn)的。數(shù)組各元素的值從文件data.txt中讀取。以下是引用片段：Optio nExplictOptionBase 1PrivateSub Form_Click()DimI AsIn teger,JAsIn teger,KAsIn tegerDimA()AsIn teger,TAsIn teger,MAsIn tegerOpe n c:mydocume nts2000testdata.txtForIn putAs #1Do

21、While (1)I=I+1Redim Preserve A(I)In put#1,A(I)LoopM=1:T= (2)Do WhileMI=M+1Do WhileI以下是引用片段：Option Base 1Private Sub Comma nd1_Click()Dim a(10) As In teger,i As In tegerFor i1 To 10a(i) = Int(Rnd * 10)+1Text1 = Text1 & Str(a(i)Next iCall shaker_sort(a)For i = 1 To 10Text2 = Text2 & Str(a(i)Next iEnd

22、SubPrivate Sub Shaker_sort(k() As Integer)IntegerDim i As Integer,cAs Integer,d AsDim t As Integerc = 1d = (1)DoFor (2) Step-1If k(i=1)k(i) Thent = k(i-1):k(i-1) = k(i):k(i) = tEnd IfNext i(3)For i = c+1 To dIf (4) Thent = k(i-1):k(i-1) = k(i):k(i) = tEnd IfNext id = d-1Loop While (5)End Sub2) 編程題 把

23、文本框輸入的字符串按降序添加到列表框中。工程X該宇符串己經(jīng)存在，諳重新輸入辛Il菇苗ni約數(shù)因子i算法說明1)最大公約數(shù)：用輾轉(zhuǎn)相除法求兩自然數(shù)m n的最大公約數(shù)。(1) 首先，對于已知兩數(shù) m n,比較并使得 mn;(2) m除以n得余數(shù)r;(3) 若r=0,則n為求得的最大公約數(shù)，算法結(jié)束；否則執(zhí)行步驟(4)m?n n?r 再重復執(zhí)行(2)譬如：10與5分析步驟：m=10 n=5r=m mod n=0所以n(n=5)為最大公約數(shù)24與9分析步驟：Word-WRAP: break-word bgColor=#f3f3f3以下是引用片段：m=24n=9r=m mod n=6r 工0 m=9 n

24、=6r=m mod n=3r 工0 m=6 n=3r=m mod n=0所以n(n=3)為最大公約數(shù) 算法實現(xiàn)循環(huán)實現(xiàn)以下是引用片段:Private Function GCD(ByVal m As Long, ByVai n As Long) As LongDim temp As LongIf m n Then temp = m: m = n: n = tempDim r As LongDor = m Mod nIf r =0 The n Exit Dom = nn = rLoopGCD = nEnd Function遞歸實現(xiàn)以下是引用片段:PrivateFunctionGCD(ByVal m

25、 As Long, ByVai n As Long) As LongDim temp As LongIf m 以下是引用片段：Opti onExplicitPrivate Function gcd( (1) As In tegerDim r As In tegerr = m Mod nIf r =0 The ngcd = nElsem = n: n = rEnd IfEnd FunctionPrivate Sub Comma nd1_Click()Dim n As In teger,p As In tegern = Val(Text1)For p = n -1 To 2 Step -1If (

26、3)The n List1.Addltem pNext pEnd Sub2)編程題生成一個三行八列的二維數(shù)組A(3,8)，其中前兩行元素產(chǎn)生的方法是：用初值 X仁26 及公式 Xi+1=(25 XXi+357) Mod 10 24,產(chǎn)生一個數(shù)列：X1、X2、.X16。其中X1X8作為A的第一行元素；X9X16作為A的第二行元素;A的第三行元素值取前兩 行同列元素的最大公約數(shù)。最后按圖示格式顯示在圖片框中。261007956705547371416 5179946317722012627631000781214327811嚴退出tL/t fQa.j獨姐生成進制轉(zhuǎn)化1i算法說明1)十進制正整數(shù) m

27、轉(zhuǎn)換為R(2-16)進制的字符串。思路：將m不斷除r取余數(shù)，直到商為 0，將余數(shù)反序即得到結(jié)果。算法實現(xiàn)：Word-WRAP: break-word bgColor=#f3f3f3以下是引用片段:PrivateFu nction Tran (ByVaimAsIn teger,ByVal r As In teger) As StringDimStrDtoRAs Strin g,nAsIn tegerDo While m on = m Mod rm = m rIf n 9 The nStrDtoR = Chr(65 + n -10)& StrDtoRElseStrDtoR = n & StrDto

28、REnd IfLoopTran = StrDtoREnd Fun cti on2) R(2-16)進制字符串轉(zhuǎn)換為十進制正整數(shù)。思路：R進制數(shù)每位數(shù)字乘以權值之和即為十進制數(shù)。算法實現(xiàn)：以下是引用片段：PrivateFu nctionTran (ByVal s As Stri ng, ByVal r As In teger)As integerDim n As In teger, dec As In tegers = UCase(Trim(s)For i% =1 To Len(s)If Mid(s, i, 1)= AThe nn=Asc(Mid(s,i,1)- Asc(A) +10Elsen=Val(Mid(s,i,1)End Ifdec = dec + n * r A (Le n(s)- i)Next iTran = decEnd Fun cti on解題技巧進