Thanks for your contribution.
I just started to learn about the Wolfram language, I'm always coding in .NET (and, more specifically, in VB.NET, because I can do everything I want with it), and could use your examples to debug my try-outs in VB.NET. Which worked out nice.
As for the backtracking algorithm in the end: I found it difficult to decipher. I tried my own, it worked, and I can read and understand the VB.NET code with not much effort. As for your Wolfram language version, I found it pretty much incomprehensible. Debet to my lack of knowledge of the Wolfram language, I know.
Thank you for your code, it did help me very much, and it looks like a tour de force! But I prefer VB.NET to enhance my Suguru/Tectonic application. Much more friendly.