程式人雜誌 -- 2014 年 3 月號 (開放公益出版品)

Visual Basic 6.0:大整數運算 加法與乘法 (使用 Array 字串) (作者：廖憲得 0xde)

大整數加法

Private Sub Command1_Click()
    Text3 = ""
    ReDim TempArray(999)
    
    K = 0
    
    For i = Len(Text1) To 1 Step -1
        TempArray(K) = Mid(Text1, i, 1)
        K = K + 1
    Next i
    
    K = 0
    
    For i = Len(Text2) To 1 Step -1
        Temp = Val(TempArray(K)) + Val(Mid(Text2, i, 1))
        TempArray(K) = Temp Mod 10
        K = K + 1
        TempArray(K) = Val(TempArray(K)) + Val(Temp \ 10)
    Next i
        
    For i = 0 To UBound(TempArray)
        If Val(TempArray(i)) > 9 Then
            Temp = TempArray(i)
            TempArray(K) = Temp Mod 10
            K = K + 1
            TempArray(K) = Val(TempArray(K)) + Val(Temp \ 10)
        End If
    Next i
        
    For i = UBound(TempArray) To 0 Step -1
        Text3 = Text3 & TempArray(i)
    Next i
    
    Do Until Val(Mid(Text3, 1, 1)) <> 0
        Text3 = Mid(Text3, 2)
    Loop
End Sub

大整數乘法

Private Sub Command1_Click()
    Text3 = ""
    ReDim TempArray(999)
    
    K = 0
    
    For i = Len(Text1) To 1 Step -1
            NowIndex = K
        For j = Len(Text2) To 1 Step -1
            Temp = TempArray(NowIndex) + Mid(Text1, i, 1) * Mid(Text2, j, 1)
            TempArray(NowIndex + 1) = Temp \ 10 + TempArray(NowIndex + 1)
            TempArray(NowIndex) = Temp Mod 10
            NowIndex = NowIndex + 1
        Next j
            K = K + 1
    Next i
    
    For i = UBound(TempArray) To 0 Step -1
        Text3 = Text3 & TempArray(i)
    Next i
    
    Do Until Val(Mid(Text3, 1, 1)) <> 0
        Text3 = Mid(Text3, 2)
    Loop
End Sub

【本文作者為「廖憲得」，原文網址為： http://www.dotblogs.com.tw/0xde/archive/2013/11/13/129111.aspx 與 http://www.dotblogs.com.tw/0xde/archive/2013/11/13/129101.aspx ，由陳鍾誠編輯後納入本雜誌】