Option Explicit
Private tmr As CTiming
Private Sub Form_Load()
Dim x       As Long
Dim vItem   As Variant
Const limit = 5000
Dim TestResults$(2)
 
    Set tmr = New CTiming
    tmr.Reset
    For x = 0 To limit
        Call FactorizadorBlackZeroX(x)
    Next x
    TestResults$(0) = tmr.sElapsed
    tmr.Reset
    For x = 0 To limit
        Call iFactorize(x)
    Next x
    TestResults$(1) = tmr.sElapsed
    tmr.Reset
    For x = 0 To limit
        Call FactorizadorFFernandez(x)
    Next x
    TestResults$(2) = tmr.sElapsed
    MsgBox "FactorizadorBlackZeroX: " & TestResults$(0) & vbCrLf & _
           "iFactorize: " & TestResults$(1) & vbCrLf & _
           "FactorizadorFFernandez: " & TestResults$(2)
End Sub
 
Public Function iFactorize(ByVal n As Long) As Collection
    Dim cTmp    As New Collection
    Dim i       As Long
    Dim lSqrt   As Long
 
    If Not n > 0 Then GoTo Ret
 
    lSqrt = Sqr(n)
 
    For i = 2 To lSqrt
        If n Mod i = 0 Then
            Set cTmp = iFactorize(n / i)
            cTmp.Add i
            GoTo Ret
        End If
    Next i
 
    cTmp.Add n
 
Ret: Set iFactorize = cTmp
End Function
 
Public Function FactorizadorFFernandez(ByVal vNumber As Long) As String
Dim i As Long
    If vNumber <= 0 Then Exit Function
    If vNumber Mod 2 = 0 Then
         FactorizadorFFernandez = FactorizadorFFernandez(vNumber / 2) & "," & 2
         Exit Function
    End If
    For i = 3 To Sqr(vNumber) Step 2
       If vNumber Mod i = 0 Then
           FactorizadorFFernandez = FactorizadorFFernandez(vNumber / i) & "," & i
           Exit Function
       End If
    Next i
    FactorizadorFFernandez = vNumber
End Function
 
Public Function FactorizadorBlackZeroX(ByVal vNumber As Long) As String
Dim i               As Long
    If vNumber < 0 Then Exit Function
    For i = 2 To Sqr(vNumber)
        If vNumber Mod i = 0 Then
            FactorizadorBlackZeroX = FactorizadorBlackZeroX(vNumber / i) & "," & i
            Exit Function
        End If
    Next i
    FactorizadorBlackZeroX = vNumber
End Function