How often we see "so how does that work, exactly?" when someone posts an up-to-date solution to their tricky problem. Try explaining this algorithm in the remaining 3 minutes of your lunch break!
Thanks Jeff for taking the time to write - for a brilliant algorithm - an equally brilliant explanation. Bookmarked.
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden