VB竞赛题库三

一、在你面前有一条长长的阶梯，如果你每步跨2阶，那么最后剩下一阶，如果你每步跨3阶，那么最后剩下2阶，如果每步跨5阶，最后剩4阶，只有当每少跨7阶时，最后才正好走完，一阶不剩。现在，问这条阶梯最少共有多少阶?

答：设这条阶梯最少共有X阶，根据题意，可知X+1是2、3、5的倍数，即X+1是30的倍数，所以X的最后一个数字必须是9，又因为X是7的倍数，所以循环的最低数应该是49，循环的步长至少应该是10，但又要满足是7的倍数，所以步长应该是70，故源程序如下：

Private Sub Command1_Click()

Dim x As Integer

x = 49

Do

 If (x + 1) Mod 30 = 0 Then Exit Do

 x = x + 70

Loop Until (1)

Label1.Caption = "这条阶梯至少共有" & x & "阶！"

End Sub

 

二、编程验证：任意一个大于9的整数，减去它的各位上的数字之和所得的差，一定能被9整除。证明中应显示从键盘输入的数，以及差值和商的过程。
（例： 123——1+2+3=6——123-6=117——117/9=13）

答：

源程序：

Private Sub Command1_Click()

Dim sum As Integer, i As Integer

Dim s As String, str As String

s = Trim(Text1.Text)

If Val(s) <= 9 Then

 MsgBox "所输入的数小于9，请重新输入!"

 Text1 = ""

 Text1.SetFocus

 Exit Sub

End If

For i = 1 To Len(s)

 sum = sum + Mid(s, i, 1)

 str = str & Mid(s, i, 1) & "+"

Next

str = Mid(str, 1, Len(str) - 1)

 

If (Val(s) - sum) Mod 9 = 0 Then

 Text2.Text = Val(s) & "——" & str & "=" & sum & "——" & Val(s) & "-" & sum & "=" & Val(s) - sum & "——" & Val(s) - sum & "/9=" & (Val(s) - sum) / 9

End If

End Sub

 

Private Sub Command2_Click()

Text1.Text = ""

Text2.Text = ""

Text1.SetFocus

End Sub

三、输入一串字符，以“？”结束，统计各字母出现的次数，并按字母出现的多少输出。（先输出字母出现次数多的，次数相同的按字母表顺序输出，不出现的字母不输出。）

答：源程序：

Private Sub Command1_Click()

Dim s As String, a(26) As Integer, i As Integer, j As Integer, n As Integer

s = Trim(Text1.Text)

s = UCase(s)

n = InStr(s, "?")

If n = 0 Then

 MsgBox "请输入结束符号？"

 Text1.SetFocus

 Exit Sub

End If

For i = 0 To n - 2

 t = Mid(s, i + 1, 1)

 t = Asc(t) - 65

 a(t) = a(t) + 1

Next

 

For j = 0 To 25

l = 0

For i = 1 To 25

    If a(i) > a(l) Then l = i

Next

If a(l) <> 0 Then List1.AddItem "字母" & Chr(65 + l) & "出现的次数为：" & a(l)

a(l) = 0

Next

End Sub

 

Private Sub Command2_Click()

Text1 = ""

List1.Clear

Text1.SetFocus

End Sub

四、编写程序，将14人（分别用A、B、C、……，N表示）随机分配在5排（每排3座）的座位中，分配后空的座位用“EMPTY”表示，并打印出座位分配情况。

答：源程序：

Dim b(15) As String

Private Sub Command1_Click()

Randomize

Dim a(15) As String

Dim i As Integer, j As Integer, num As Integer

 

For i = 0 To 13

a(i) = Chr(65 + i)

Next

a(14) = "EMPTY"

For i = 0 To 14

 b(i) = "0"

Next

 

For i = 0 To 14

 num = Int(15 * Rnd)

 While cz(a(num)) = True

   num = Int(15 * Rnd)

 Wend

   b(i) = a(num)

 Next

 j = 1

 For y = 0 To 14

    If j Mod 3 = 0 Then

      Text1 = Text1 & b(y) & vbCrLf

    Else

     Text1 = Text1 & b(y) & "       "

    End If

    j = j + 1

Next

End Sub

 

Private Function cz(x As String) As Boolean

Dim i As Integer

cz = False

For i = 0 To 14

 If b(i) = x Then cz = True: Exit For

Next

End Function

Private Sub Command2_Click()

Text1 = ""

End Sub