First power of 2 that has leading decimal digits of 12: Difference between revisions

=={{header|Visual Basic .NET}}==

<lang vbnet>Module Module1

Function Func(ByVal l As Integer, ByVal n As Integer) As Long

Dim res As Long = 0, f As Long = 1

Dim lf As Double = Math.Log10(2)

Dim i As Integer = l

While i > 10

f *= 10

i /= 10

End While

While n > 0

res += 1

If CInt((f * Math.Pow(10, res * lf Mod 1))) = l Then

n -= 1

End If

End While

Return res

End Function

Sub Main()

Dim values = {Tuple.Create(12, 1), Tuple.Create(12, 2), Tuple.Create(123, 45), Tuple.Create(123, 12345), Tuple.Create(123, 678910), Tuple.Create(99, 1)}

For Each pair In values

Console.WriteLine("p({0,3}, {1,6}) = {2,11:n0}", pair.Item1, pair.Item2, Func(pair.Item1, pair.Item2))

Next

End Sub

End Module</lang>

{{out}}

<pre>p( 12, 1) = 60

p( 12, 2) = 70

p(123, 45) = 12,710

p(123, 12345) = 3,496,509

p(123, 678910) = 192,278,374

p( 99, 1) = 93</pre>