Random thoughts, tips & tricks about Slackware-Linux, Lego and Star Wars

SuDoKu revisited

November 8th, 2012 by Niels Horn in

Way back, in January 2006, I wrote an Excel macro in VBA on a quiet day to solve SuDoKu puzzles. At the time I thought it was flawless, as it solved each and every puzzle I entered.
Some time later, I published the macro on and challenged people to find puzzles that my macro could not solve. Many people downloaded the macro but things stayed quiet, apart from the occasional "thank you" e-mail…

But then, almost five years later, I received the first report about an extremely difficult puzzle that could not be solved. Unfortunately, I was too caught up with work at the time to really dig into it. And then things got quiet again…

But suddenly, a few weeks ago, I received another e-mail about a puzzle that resulted in an erroneous solution. And then another one, from a different visitor. This started me thinking.

I don't even use Excel anymore at home (switched completely to LibreOffice), but I got curious enough to get my old Office 2000 CD and install it on my virtual Windows machine.
After some serious testing, I found the bug (and another one that was reported) and - after almost seven years and more than 2.500 downloads - updated my VBA macro and published it on my site.

The new version is for anyone to test and the challenge is open again: Find a puzzle that cannot be solved with my macro and I'll publish your name on my site (and improve the macro again).
Let's see if it will take another six years to find a flaw :)