Dim Shared As Byte n, d, best(16)

Sub TrySwaps(A() As Byte, f As Byte, s As Byte)
    Dim As Byte B(16), i, j, k
    If d > best(n) Then best(n) = d
    Do
        If A(s) = -1 Or A(s) = s Then Exit Do
        If d+best(s) <= best(n) Then Exit Sub
        If s = 0 Then Exit Do
        s -= 1
    Loop

    d += 1
    For i = 0 To s
        B(i) = A(i)
    Next

    k = 1
    For i = 1 To s
        k Shl= 1
        If B(i) =- 1 AndAlso (f And k) = 0 Or B(i) = i Then
            j = i
            B(0) = j
            While j
                j -= 1
                B(i-j) = A(j)
            Wend
            TrySwaps(B(), f Or k, s)
        End If
    Next
    d -= 1
End Sub

Dim As Byte i, X(16)
For i = 0 To 16-1
    X(i) = -1
    best(i) = 0
Next  i
X(0) = 0

For n = 1 To 13
    d = 0
    TrySwaps(X(), 1, n-1)
    Print Using "##: ##"; n; best(n)
Next n

Sleep