To all sudoku gods, please help.

defunct · Posted: Mon Oct 02, 2006 9:23 pm Post subject: To all sudoku gods, please help.

Hello everyone, thanks for taking the time to read my post.
My company is organizing a nationwide challenge consisting of many challenges and whoever is first to clear all stages will get a top prize.

One of the challenges for participants involve solving a sudoku puzzle. I have a couple of questions regarding that:

- is it possible to devise a unique sudoku that cannot be solved by
computer programs (or at the very least, take a very long time by programs to solve)?
- to prevent people from cheating (i.e using computer programs), should I devise alternative sudokus such as 16 by 16 or 25 by 25 ones? Or should I use symbols to replace the numbers or does it not make a difference for cheaters?
- does anyone have any advice regarding how I should go about setting the sudoku challenge?

Thanks again for reading. I am not a programmer so please reply in layman's terms when possible.

Cheers.

m_b_metcalf

Soultaker · Posted: Tue Oct 03, 2006 10:46 pm Post subject:

I think high-rank puzzles are generally 'more' harder for human players than computers, if you get what I mean. I remember solving a 25x25 (!) puzzle programmatically; that took a minute where regular puzzles take less then a second, but solving it by hand would have been practically impossible. So, creating a larger puzzles makes it harder for both the computer and human solvers, but more so for the latter. I wouldn't recommend it.

Using a non-standard variation is a good idea, though. Although you can't prevent people from solving it with the computer altogether, you can at least prevent the use of any standard programs available today. For example, you could create a shape sudoku (one where the 3x3 blocks are replaced with arbitrary shapes) and combine it with a diagonal sudoku (where the digits on the diagonals must be all different).

For something completely different, you could take a look at the Exotic Sudoku subforum; many people have proposed variants that are pretty different from Sudoku as you know it, and I doubt solvers exist for most of them. Ofcourse, the question is wether or not you insist on including a Sudoku puzzle; you could include an exotic variant, but that wouldn't really be a sudoku puzzle anymore.

defunct · Posted: Wed Oct 04, 2006 6:14 am Post subject: Need help

Thanks, Mike and Soultaker for replying.

Do you think it is better to use a butterfly/ samurai sudoku or just a plain 25X25 one?

I want an extremely hard puzzle but at the same time, one that is solvable after a very long time and a fair bit of mean thinking.

The butterfly/ samurai sudoku seems like a very interesting variant.
I would love to use it in the latter stages of my challenge if you think it is a difficult enough variant.

How long does it take for an expert to solve a butterfly/ samurai puzzle?

Can anyone please devise a unique butterfly/ samurai sudoku for me?

I will include your name in the writing credits of the mystery if I were to
use any of your work.

Thanks again in advance. Very Happy

m_b_metcalf · Posted: Wed Oct 04, 2006 12:50 pm Post subject: Re: Need help

daj95376 · Posted: Wed Oct 04, 2006 1:36 pm Post subject:

It seems to me that your insisting on having a complicated Sudoku puzzle in your contest will lead to one of two possible outcomes:

1) Someone with access to an advanced solver will win your contest, or
2) No one will be able to win your contest.

If (2) is your objective, then substitute FreeCell Pro's (FcPro) deal #53687601 for the Sudoku puzzle. In the first 100,000,000 8x4 FcPro deals, this is the only deal that has never been resolved as solvable/unsolvable.

defunct · Posted: Wed Oct 04, 2006 3:33 pm Post subject: unique sudoku needed

I do not wish to create a puzzle that no one will be able to solve.
Just one that even experts will take quite a while to solve.
The sudoku is not the be all and end all in the contest. There are other stages that people with advanced programs will have to solve as well so it doesn't follow that whoever has an advanced solver will win the competition though that will be a huge advantage.

Mike, if you are interested in supplying us with sudoku puzzles, please
get in touch with me at cliff.gay@gmail.com or add me to your MSN using the email contact defunct21@hotmail.com and we can discuss how we can
work together.

Soultaker · Posted: Thu Oct 05, 2006 12:52 pm Post subject:

Maybe you should have a look at Ruud's clueless (not really) puzzles in the Exotic Sudoku forum. They are:
- hard to solve by hand, but not as tedious as large (25x25) regular puzzles,
- very similar to Sudoku, gameplay-wise,
- non-standard enough so there is no solver available (ok, Ruud probably has a solver).

Either way, I think the way to go is to pick a non-standard variant, not a large regular sudoku. The large regular sudoku's are still easily solved programmatically, but tedious to do by hand. But it's your call ofcourse; if you have your mind set on a 25x25 Sudoku I won't stop you. Smile

defunct · Posted: Fri Oct 06, 2006 6:06 am Post subject:

I'm thinking of a 25X25 because it's really difficult to solve and I can't find any solvers online using google. But you're probably right, a lot of people could probably break it easily with their own solvers.

What do you think are some of the more interesting variants?

Ruud · Site Admin

There are many solvers that cannot be found by Google, simply because they are not publicly available. Many members of this forum have written their own solver, but only a few make them available to others. This does not only apply to solvers for 9x9 sudoku, but also for other sizes. I have a solver/generator that can handle every size upto 16x16, but it takes me 2 minutes to modify it to handle 25x25.

Human players are not so lucky. 25x25 will not attract many players, because you cannot manage 625 cells as a human player. Unlike a Clueless or Samurai, you cannot isolate any part of the puzzle. The few people with computer solvers would have an even greater advantage.

Check Pyrrhon's variant page to check out some exotic variants. You can mix any number of constraints to come up with a new variant. But even if you create something new, there will always be people who can adapt their software for it. You need to stay one step ahead all the time.

Ruud
_________________
Meet me at sudocue.net

tarek · Posted: Sat Oct 07, 2006 12:59 am Post subject:

How about this,

Pick a puzzle know to have MULTIPLE SOLUTIONS or even NO SOLUTION...........

in order to establish the staus of the above you have to use very advanced techniques or a computer solver........

You are after the first few placements the a person can manage before getting stuck.... not knowing even that this puzzle is INVALID......

so you would know that for example r1c1....r5c6 can be uncovered using singles regardless of the staus of the grid any other placemnt need far more advanced techniques....No one would know the staus of the grid unless he cheated......

In the competition ask for the first 2 placements & if it matches the above then you've got a winner....Any other answer (which may be correct) would be a cheat, guesser.........

Not watertight, but tough to get around for a surprised cheat.

tarek

Jean-Christophe · Posted: Sun Oct 08, 2006 2:52 pm Post subject:

I agree 100% with Ruud Cool

Have a look at combined sudokus like this one

There are probably no software which will solve such a variant.
_________________
Jean-Christophe
"When you have eliminated the impossible, whatever remains, however improbable, must be the truth." Sherlock Holmes.

defunct · Posted: Tue Oct 10, 2006 7:14 am Post subject:

Ruud, I think you are right. A 25X25 puzzle will probably drive someone crazy. I was thinking of using a butterfly samurai puzzle but what do you think of my using that variant? Is is suitable?

Tarek, your suggestion is excellent but unfortunately it will be hard to execute that as none of us are expert sudoku solvers (much less setters).

Jean, the combined sudokus seem like a very interesting option as well.
Will any of you be willing to contribute your own puzzles to us?

Jean-Christophe · Posted: Tue Oct 10, 2006 8:07 am Post subject:

m_b_metcalf · Posted: Tue Oct 10, 2006 12:18 pm Post subject: