2020年8月6日 星期四

vb.net 將數字轉成羅馬數字 [Convert number to roman numerals] 

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    Public Function ConvertToRomanNumber(ByVal value As Integer) As String
        Dim romanNumber As New System.Text.StringBuilder()
        If value > 0 AndAlso value < 5000 Then
            Dim valueString As String = value.ToString()
            Dim thousands As Integer = value \ 1000
            Dim hundreds As Integer = (value Mod 1000) \ 100
            Dim dozens As Integer = (value Mod 100) \ 10
            Dim units As Integer = value Mod 10
            romanNumber.Append(ConversionHelper(thousands, 4))
            romanNumber.Append(ConversionHelper(hundreds, 3))
            romanNumber.Append(ConversionHelper(dozens, 2))
            romanNumber.Append(ConversionHelper(units, 1))
        Else
            romanNumber.Append("Value is out of range. Valid range is 1-4999")
        End If
        Return romanNumber.ToString()
    End Function






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    Private Function ConversionHelper(ByVal digit As Integer, ByVal position As Integer) As String
        Dim retVal As New System.Text.StringBuilder()

        Dim romanLetterList As New List(Of Char())
        romanLetterList.Add(New Char() {"I"c, "V"c})    '1, 5
        romanLetterList.Add(New Char() {"X"c, "L"c})    '10, 50
        romanLetterList.Add(New Char() {"C"c, "D"c})    '100, 500
        romanLetterList.Add(New Char() {"M"c, "?"c})    '1000, ? (No char symbol for 5000)

        If position = 4 Then
            retVal.Append(romanLetterList(position - 1)(0), digit)
        Else
            Select Case digit
                Case 0 To 3
                    retVal.Append(romanLetterList(position - 1)(0), digit)
                Case 4
                    retVal.Append(romanLetterList(position - 1)(0), 1)
                    retVal.Append(romanLetterList(position - 1)(1), 1)
                Case 5
                    retVal.Append(romanLetterList(position - 1)(1), 1)
                Case 6 To 8
                    retVal.Append(romanLetterList(position - 1)(1), 1)
                    retVal.Append(romanLetterList(position - 1)(0), digit - 5)
                Case 9
                    retVal.Append(romanLetterList(position - 1)(0), 1)
                    retVal.Append(romanLetterList(position)(0), 1)
            End Select
        End If
        Return retVal.ToString()
    End Function
於
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