Question

How to count the number of digits in an integer with VB.NET

Answer 1

Imports System

Module DigitCounterLog10

    ' Counts digits using Math.Log10.
    ' Uses the formula: floor(log10(n)) + 1
    ' Zero is handled separately because log10(0) is undefined.
    Function CountDigitsLog10(value As Integer) As Integer
        Dim num As Integer = Math.Abs(value)

        If num = 0 Then
            Return 1
        End If

        Return CInt(Math.Floor(Math.Log10(num))) + 1
    End Function

    Sub Main()
        Dim number As Integer = 987654321

        Dim digits As Integer = CountDigitsLog10(number)

        Console.WriteLine("Number: " & number)
        Console.WriteLine("Digit count (log10 method): " & digits)
    End Sub

End Module


' run:
' 
' Number: 987654321
' Digit count (log10 method): 9
'

 

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Answer 2

Imports System

Module DigitCounterString

    ' Returns the number of digits in an Integer using string conversion.
    ' This approach is clear, safe, and works well for everyday use.
    Function CountDigitsString(value As Integer) As Integer
        Dim text As String = value.ToString()

        ' If the number is negative, ignore the leading "-" sign
        If text.StartsWith("-") Then
            Return text.Length - 1
        End If

        Return text.Length
    End Function

    Sub Main()
        Dim number As Integer = -12345

        Dim digits As Integer = CountDigitsString(number)

        Console.WriteLine("Number: " & number)
        Console.WriteLine("Digit count (String method): " & digits)
    End Sub

End Module



' run:
'
' Number: -12345
' Digit count (String method): 5
'

 

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