The New Sudoku Players' Forum

by **saulysw** » Tue Aug 02, 2005 12:08 pm

Hello everyone!

I would like to invite you to have a look at web page I wrote, which explains Sudoku solving techniques and also gives a quick tutorial. It is meant largely for beginners, but there are tips on advanced techniques as well.

http://www.users.bigpond.net.au/sbryan/other/sudoku.html

I am happy to get any feedback! You may well know some tricks that I don't know....

Regards,
Saul

by **george-no1** » Tue Aug 02, 2005 12:20 pm

Hi saulysw

I think all the basic techniques are there, but for the sake of completeness you may want to include the X-Wing, which although not needed for some hard puzzles, can prove useful and time-saving.

Of course there are other techniques that you haven't included which are rare/non-existent in even the harder puzzles, for example Swordfish and XY-Wing (both building on X-Wing), Colouring, and *slightly* trial-and-error-ish techniques such as Nishio and Forcing Chains.

However, if you only want it to be for beginners to moderate players, you should probably ignore everything above except the X-Wing.

George

by **Nick70** » Tue Aug 02, 2005 12:29 pm

george-no1 wrote:Of course there are other techniques that you haven't included which are rare/non-existent in even the harder puzzles, for example Swordfish and XY-Wing (both building on X-Wing), Colouring, and *slightly* trial-and-error-ish techniques such as Nishio and Forcing Chains.

And the Turbot fish! Don't forget the turbot fish! It's more common than x-wing, swordfish and xy-wing put together!

by **george-no1** » Tue Aug 02, 2005 12:33 pm

OK OK I'm sorry Nick70. I didn't mean to leave you out, I know the Turbot Fish is important. I was only putting together a brief list of the advanced techniques that I could remember off the top of my head. I only forgot to include it because I've never needed to use it.

Is it really more common than X-Wing and its derivatives? I don't know how you could quantify common-ness.

George

by **saulysw** » Tue Aug 02, 2005 12:42 pm

Guys,

Thanks for your replies - I'll check those techniques out....!

- Saul

by **Nick70** » Tue Aug 02, 2005 12:50 pm

george-no1 wrote:Is it really more common than X-Wing and its derivatives? I don't know how you could quantify common-ness.

Well, I have generated and rated a number of problems (almost 100,000 at this point).

Admittedly, they are all based on the same 21-cell intial pattern of hints, so they might not be statistically representative of the whole set of sudoku puzzles.

However, in that set of puzzles I have:

185 x-wing
109 swordfish
3174 xy-wing
4432 turbot fish

so as you can see it's immensely more common than x-wing or swordfish.
I'm using it all over the place when solving hard puzzles, and I've actually put it just above x-wing in my difficulty rating scale (before triplets and swordfish).

by **Karyobin** » Tue Aug 02, 2005 5:47 pm

So it would seem that common-ness can be quantified by there being more of one thing than other things.

Odd that. ;-]

by **tso** » Tue Aug 02, 2005 6:11 pm

Nick70 wrote:... they are all based on the same 21-cell intial pattern of hints ...

Why do you use the same pattern?

by **Nick70** » Tue Aug 02, 2005 7:25 pm

tso wrote:Why do you use the same pattern?

Because I'm interested in seeing how the puzzles vary by just changing the value of the hints and not their position. And I also want to see if there is a 18-hints puzzle hidden among all the ones based on this pattern (only 19 and 20 for now).

Unfortunately I won't finish the search in this lifetime.

by **george-no1** » Wed Aug 03, 2005 9:51 am

tso wrote:
george-no1 wrote:... they are all based on the same 21-cell intial pattern of hints ...

tso, I didn't write that, it was Nick70.

by **snapdragon** » Thu Aug 04, 2005 1:34 pm

I am pretty adept at the basic Sudoku techniques which are so nicely described in Saul's website etc., but I am looking for more advanced techniques and so I came here. Problem: I can't understand how to read the "grid" that people use on this forum. Am I the only dummy?

Upshot: I would love to see an extension of the techniques site that covers all those fish and wings!

by **george-no1** » Thu Aug 04, 2005 1:48 pm

snapdragon,

what do you mean by 'the grid that people use'? If you're referring to

...l...l...
...l...l...
...l...l...
---------
...l...l...
...l...l...
...l...l...
---------
...l...l...
...l...l...
...l...l...

or something similar without the ''- and the 'l' then you just have to imagine that they're there.

For the fish and wings, you could try simes' site or angusj's site, whose addresses are posted all over the forum and in their profiles. I'm going to be writing my own explanation of the fish and wings, but the only problem is I have no website to put it on; I might have to post it as a Word document or something similar once I have finished.

George