Question

How to check whether the number has only first and last bits set in VB.NET

Answer 1

Imports System
 
Public Class Test
    Public Shared Function is_only_first_and_last_bit_set(n as integer)
        return ((n - 1) And (n - 2)) = 0
    End Function
     
    Public Shared Sub Main()
        Dim n as Integer = 129
         
        Console.WriteLine(Convert.ToString(n, 2).PadLeft(8, "0"C))
        Console.WriteLine(Convert.ToString(n - 1, 2).PadLeft(8, "0"C))
        Console.WriteLine(Convert.ToString(n - 2, 2).PadLeft(8, "0"C))
        Console.WriteLine(Convert.ToString((n - 1) And (n - 2), 2).PadLeft(8, "0"C))
        
        if (is_only_first_and_last_bit_set(n)) Then
            Console.WriteLine("Yes")
        else
            Console.WriteLine("No")
        End If

    End Sub
End Class
 
 
'run:
 
' 10000001
' 10000000
' 01111111
' 00000000
' Yes

 

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