VB常用算法（四）进制转化- -

曹苏群  http://caosuqun.bokee.com

1、算法说明

1)        十进制正整数m转换为R（2－16）进制的字符串。

         思路： 将m不断除r取余数，直到商为0，将余数反序即得到结果。

         算法实现：

Private Function Tran(ByVal m As Integer, ByVal r As Integer) As String

    Dim StrDtoR As String, n As Integer

    Do While m <> o

        n = m Mod r

        m = m \ r

        If n > 9 Then

            StrDtoR = Chr(65 + n - 10) & StrDtoR

        Else

            StrDtoR = n & StrDtoR

        End If

    Loop

    Tran = StrDtoR

End Function

2)        R（2－16）进制字符串转换为十进制正整数。

         思路：R进制数每位数字乘以权值之和即为十进制数。

         算法实现：

Private Function Tran(ByVal s As String, ByVal r As Integer) As integer

    Dim n As Integer, dec As Integer

    s = UCase(Trim(s))

    For i% = 1 To Len(s)

               If Mid(s, i, 1) >= "A" Then

                        n = Asc(Mid(s, i, 1)) - Asc("A") + 10

               Else

                        n = Val(Mid(s, i, 1))

               End If

               dec = dec + n * r ^ (Len(s) - i)

    Next i

    Tran = dec

End Function

解题技巧

         进制转化的原理要清楚,同时编写代码时候要留意16进制中的A－F字符的处理。

2、实战练习

1)        补充代码（2002秋二（9））

         本程序是把给定的二进制整数转换为八进制整数。

                  Private Sub Command1_Click()

                           Dim a As String, b As String, c As String

                           Dim L As Integer, m As Integer, n As Integer

                           a = InputBox("请输入一个二进制数", "输入框")

                              （1）    

                           a = String(L, "0") & a

                              （2）    

                           For m = 1 To n / 3

                             b = Mid(a, 3 * m - 2, 3)

                                 （3）     

                           Next m

                           Text1.Text = c

                  End Sub

                  Private Function zh(s As String) As String

                           Dim i As Integer, n As Integer, p As Integer

                           p = 1

                           For i = 2 To 0 Step -1

                                       （4）     

                              p = p + 1

                           Next i

                           zh = Str(n)

                  End Function

2)        补充代码（2001春二（7））

         下面程序是把给定的16进制正整数转换为10进制数。

                  Option Explicit

                  Private Sub Form_Click()

                           Dim St As Integer， Dem As Long

                           St=InputBox("输入一个十六进制数")

                           Dem=Convert(St)

                           Print St; ">="; Dem

                  End Sub

                  Private Function Convert(S As String)As Long

                           Dim N As Integer， I As Integer，Substring As String*1

                           Dim P As long， K As Long，Asc1 As Integer

                           N=  （1）  

                           P=16^N

                           For I=1 To N

                                    P=P/16

                                    Substring=  （2）  

                                    Select Case Substring

                                             Case "0" To "9"

                                                      K=K+P*Val(Substring)

                                             Case   （3）  

                                                      Asc1=Asc(Substring)-Asc("A")+10

                                                        （4）  

                                    End Select

                           Next I

                             （5）  

                  End Function