二級(jí)vb考試系統(tǒng)第3次課循環(huán)(14學(xué)時(shí))

1、2010年9月等級(jí)考試輔導(dǎo)二級(jí)Visual Basic1第三講 VB控制結(jié)構(gòu)-循環(huán)列表框、組合框2當(dāng)循環(huán)控制結(jié)構(gòu)3Do循環(huán)控制結(jié)構(gòu)4常用算法 6For循環(huán)控制結(jié)構(gòu)1多重循環(huán)5考點(diǎn)3 For循環(huán)控制結(jié)構(gòu) For 循環(huán)變量 = 初值 To 終值 step 步長循環(huán)語句塊 Exit ForNext 循環(huán)變量For i = 1 To 2 step 1Form1.Print iNext iFor i = 1 To 2 step 1Form1.Print iNext ii=1i=2True考點(diǎn)3 For循環(huán)控制結(jié)構(gòu)For i = 1 To 2 step 1Form1.Print iNext ii=1i=2

2、Form1.Print iTrue考點(diǎn)3 For循環(huán)控制結(jié)構(gòu)For i = 1 To 2 step 1Form1.Print iNext ii=1i=2Form1.Print iTruei = i + 1考點(diǎn)3 For循環(huán)控制結(jié)構(gòu)For i = 1 To 2 step 1Form1.Print iNext ii=1i=2Form1.Print iTruei = i + 1考點(diǎn)3 For循環(huán)控制結(jié)構(gòu)For i = 1 To 2 step 1Form1.Print iNext ii=1i 10 Then Exit For Next Text1.Text = Str(n)End Sub程序運(yùn)行后，單

3、擊命令按鈕，在文本框中顯示的值是（ ）（A）5 （B）4 （D）22006年9月選擇題第19題 （C）3在窗體上畫一個(gè)命令按鈕，其名稱為Command1，然后編寫如下事件過程： Private Sub Command1_Click() Dim i As Integer, x As Integer For i = 1 To 6 If i = 1 Then x = 1 If i = 0 And score = 90 Then y = y + 1 ElseIf score = 80 Then l = l + 1 ElseIf score = 70 Then z = z + 1 ElseIf scor

4、e = 60 Then j = j + 1 Else b = b + 1 End If total = total + 1score = Val(InputBox(請輸入成績)為計(jì)算1+3+5+99的值，某人編程如下k=1s=0Whilek=99k=k+2 s=s+kWendPrints在調(diào)試時(shí)發(fā)現(xiàn)運(yùn)行結(jié)果有錯(cuò)誤，需要修改。下列錯(cuò)誤原因和修改方案中正確的是（ ）(A)WhileWend循環(huán)語句錯(cuò)誤，應(yīng)改為Fork=1To99Nextk(B)循環(huán)條件錯(cuò)誤，應(yīng)改為Whliek99(C)循環(huán)前的賦值語句k=1錯(cuò)誤，應(yīng)改為k=0(D)循環(huán)中兩條賦值語句的順序錯(cuò)誤，應(yīng)改為s=s+k:k=k+22007年

5、4月選擇題27題解題思路：1.查找出錯(cuò)位置檢查前1個(gè)數(shù)和后1個(gè)數(shù)是否參加運(yùn)算； 有無多余的數(shù)參加運(yùn)算。2.確定修改方案直接確定法 按選項(xiàng)提示修改法考點(diǎn)5 Do循環(huán)控制結(jié)構(gòu)DoLoop循環(huán)控制結(jié)構(gòu)For i = 1 To 2 step 1Form1.Print iNext ii = 1Do While i 2 Form1.Print i i = i + 1Loopi = 1Do Form1.Print i i = i + 1Loop While i 2 score = Val(InputBox(請輸入成績) While score = 0 And score = 90 Then y = y +

6、1 ElseIf score = 80 Then l = l + 1 ElseIf score = 70 Then z = z + 1 ElseIf score = 60 Then j = j + 1 Else b = b + 1 End If total = total + 1score = Val(InputBox(請輸入成績)Do While score = 0 And score = 100LoopDo Until score 100LoopDoLoop循環(huán)控制結(jié)構(gòu)思考：本題是否適合將條件寫于Loop后？ score = Val(InputBox(請輸入成績) Do If score

7、100 Then Exit Do If score = 90 Then y = y + 1 ElseIf score = 80 Then l = l + 1 ElseIf score = 70 Then z = z + 1 ElseIf score = 60 Then j = j + 1 Else b = b + 1 End If total = total + 1 score = Val(InputBox(請輸入成績) LoopDoLoop循環(huán)2007年4月選擇題27題設(shè)有如下程序：Private Sub Command1_Click() Dim c As Integer, d As Int

8、eger c = 4 d = InputBox(請輸入一個(gè)整數(shù)) Do While d 0 If d c Then c = c + 1 End If d = InputBox(請輸入一個(gè)整數(shù)) Loop Print c + dEnd Sub 程序運(yùn)行后，單擊命令按鈕，如果在輸入對話框中依次輸入1、2、3、4、5、6、7、8、9、0，則輸出結(jié)果是_。（A）12 （B）11 （C）10（D）9For的循環(huán)嵌套考點(diǎn)6 多重循環(huán)For i = 1 To 5 For j = 1 To 5 x = x + 1 Next j Next iFor i = 1 To 5 For j = 1 To i x = x

9、 + 1 Next j Next ii1XX+1執(zhí)行的次數(shù)為55次XX+1執(zhí)行的次數(shù)為12345次For的循環(huán)嵌套For i = 1 To 5 For j = 1 To 5 x = x + 1 Next j Next iFor i = 1 To 5 For j = 1 To i x = x + 1 Next j Next ix = 1x = 1考點(diǎn)6 多重循環(huán)For的循環(huán)嵌套For i = 1 To 5 For j = 1 To 5 x = x + 1 Next j Next iFor i = 1 To 5 For j = 1 To i x = x + 1 Next j Next ix = 1

10、x = 1考點(diǎn)6 多重循環(huán)For的循環(huán)嵌套For i = 1 To 5 For j = 1 To 5 x = x + 1 Next j Next iFor i = 1 To 5 For j = 1 To i x = x + 1 Next j Next iy = y + 1y = y + 1考點(diǎn)6 多重循環(huán)考點(diǎn)7 常用算法判斷素?cái)?shù)循環(huán)?？妓惴ㄇ笞畲蠊s數(shù)最小公倍數(shù)上機(jī)考試出現(xiàn)概率較高求素?cái)?shù)算法For i = 2 To n - 1 If n Mod i = 0 Then Exit For End IfNext iIf in-1 Then Print n; 是質(zhì)數(shù)End Ifi = 2Do Whil

11、e i n - 1 Then Print n; 是素?cái)?shù)End If判斷素?cái)?shù)：依次取2,n - 1范圍內(nèi)數(shù)據(jù)與待判定數(shù)據(jù)n 取余，若余數(shù)為0，即終止，并判定n不為 素?cái)?shù)，否則若該范圍內(nèi)所有數(shù)據(jù)均不能整 除n，則n為素?cái)?shù)素?cái)?shù)：只能被1和它自身整除的整數(shù)求素?cái)?shù)算法For i = 2 To n - 1 If n Mod i = 0 Then Exit For End IfNext iIf in-1 Then Print n; 是質(zhì)數(shù)End Ifi = 2Do While i n - 1 Then Print n; 是素?cái)?shù)End If2,n - 1范圍可改為2, sqr(n) 或 2,n 2Sqr(n)

12、If i Sqr(n) thenSqr(n)If i Sqr(n) thenFlag=TrueFor i = 2 To n - 1 If n Mod i = 0 Then Flag=False End IfNext iIf Flag Then Print n; 是質(zhì)數(shù)End If求素?cái)?shù)算法flag = Truei = 2Do While i Sqr(i) Then List1.AddItem iNext i上機(jī)真題找出比給定素?cái)?shù)值小的最大3個(gè)素?cái)?shù) 求最大公約數(shù)（輾轉(zhuǎn)相除）被除數(shù)除數(shù)商余數(shù)34 0343113130u v r3與4的最大公約數(shù)實(shí)例：求3與4的最大公約數(shù)余數(shù)為0最大公約數(shù)：兩數(shù)相除，取余： r = u mod v余數(shù)為0，則gcd v余數(shù)非0，用前次除數(shù)v作被除數(shù)，余數(shù)r作除數(shù)， 再取余，并轉(zhuǎn)至判斷 即：u = v: v = r : r = u mod v 最小公倍數(shù)：lcm=uv / gcd求最大公約數(shù)u = 15: v = 5m = u: n = vDo r = u Mod v u = v v = rLoop Until r = 0Print 最大公約數(shù); u Print “最小公倍數(shù); m