Huh, it seems Bob further optimized his code. The one I remember used the similar approach, but employed a doubly-linked list for backtracking. The pleasant surprise that I got from his code was that recursion plus a linked list still beat those "faster" languages, a classical example of optimizing algorithms first, as beautifully argued in Steven Skiena's Algorithm Design Manual

Here's the one you were thinking of. This was the one "further optimized", not the first one posted:

https://web.archive.org/web/20090723015302/http://crazybob.o...

Ah, yes. Thanks!