#define STX  Chr(&H2)
#define ETX  Chr(&H3)

Sub Sort(arr() As String)
    Dim As Integer i, j, n
    n = Ubound(arr) + 1
    For i = 0 To n - 1
        For j = i + 1 To n - 1
            If arr(i) > arr(j) Then Swap arr(i), arr(j)
        Next j
    Next i
End Sub

Function Replace(Byval cadena As String, Byval subcadena As String, Byval reemplazaCon As String) As String
    Dim As Integer posic = Instr(cadena, subcadena)
    While posic <> 0
        cadena = Left(cadena, posic - 1) & reemplazaCon & Mid(cadena, posic + Len(subcadena))
        posic = Instr(posic + Len(reemplazaCon), cadena, subcadena)
    Wend
    Return cadena
End Function

Sub Rotate(s As String)
    Dim As Integer longi = Len(s)
    Dim As String t = Right(s, 1)
    s = t & Left(s, longi - 1)
End Sub

Function BWT(s As String) As String
    Dim As Integer i
    For i = 1 To Len(s)
        If Mid(s, i, 1) = STX Orelse Mid(s, i, 1) = ETX Then
            Print "ERROR: String can't contain STX or ETX";
            Exit Function
        End If
    Next i

    Dim As String ss = STX & s & ETX
    Dim As Integer longi = Len(ss)
    Dim As String tabla(longi)

    For i = 1 To longi
        tabla(i) = ss
        Rotate(ss)
    Next i

    Sort tabla()

    Dim As String salida
    For i = 1 To longi
        salida &= Right(tabla(i), 1)
    Next i

    Return salida
End Function

Function Ibwt(r As String) As String
    Dim As Integer i, j
    Dim As Integer longi = Len(r)
    Dim As String sa(1 To longi)
    Dim As String tabla(Lbound(sa) To Ubound(sa))

    For i = 1 To longi
        For j = 1 To longi
            tabla(j) = Mid(r, j, 1) & tabla(j)
        Next j
        Sort tabla()
    Next i

    For i = Lbound(tabla) To Ubound(tabla)
        If Right(tabla(i), 1) = ETX Then Return Mid(tabla(i), 2, longi - 2)
    Next i

    Return ""
End Function

Function makePrintable(s As String) As String
    Dim As String ls = s

    For i As Integer = 1 To Len(ls)
        Select Case Mid(ls, i, 1)
        Case STX : Mid(ls, i, 1) = "^"
        Case ETX : Mid(ls, i, 1) = "|"
        End Select
    Next i

    Return ls
End Function

Dim As String tests(5) = { _
"banana", "appellee", "dogwood", "TO BE OR NOT TO BE OR WANT TO BE OR NOT?", _
"SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES", STX & "ABC" & ETX }

For i As Integer = Lbound(tests) To Ubound(tests)
    Print makePrintable(tests(i))
    Print " --> ";
    Dim As String t = BWT(tests(i))
    Print makePrintable(t)
    Dim As String r = iBWT(t)
    Print " --> "; r; Chr(10); Chr(10);
Next i

Sleep