VB常用算法（四）進制轉化- -

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1、算法說明

1)        十進制正整數m轉換為R（2－16）進制的字符串。

         思路： 將m不斷除r取余數，直到商為0，將余數反序即得到結果。

         算法實現：

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）進制字符串轉換為十進制正整數。

         思路：R進制數每位數字乘以權值之和即為十進制數。

         算法實現：

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

解題技巧

         進制轉化的原理要清楚,同時編寫代碼時候要留意16進制中的A－F字符的處理。

2、實戰練習

1)        補充代碼（2002秋二（9））

         本程序是把給定的二進制整數轉換為八進制整數。

                  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("請輸入一個二進制數", "輸入框")

                              （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)        補充代碼（2001春二（7））

         下面程序是把給定的16進制正整數轉換為10進制數。

                  Option Explicit

                  Private Sub Form_Click()

                           Dim St As Integer， Dem As Long

                           St=InputBox("輸入一個十六進制數")

                           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