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Feedback and Questions

I've received a lot of interesting comments and questions from Sudoku fans over the last few years and this page is where I try to answer them. Please feel free to drop me a note on the side of the page or try the Facebook comment box. Or you can email me directly at .

Post a Comment or Question here...
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Any Sudoku you want to publish here for easy loading into the solver - 81 characters, use '.' or '0' for unknowns.

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Many thanks to all the people who have helped improve the solvers and strategies with their feedback!

Saturday 11-Nov-2006

... by: Richard Broughton, UK

Load Sudoku:

Hi

found this gem that my solver gives up on - and unfortunately so does yours (although your solver gets one further candidate reduction than mine)

Brute force will solve it - and your solution count indicates that there's only one solution.

I'd be interested to see if there is any strategy that can be applied to bring a logical conclusion to this problem


Wednesday 8-Nov-2006

... by: JC Meyrignac, France

Load Sudoku:

AI Etana ( http://www.sudoku.com/forums/viewtopic.php?t=4212 ) cannot be solved by your solver.
Any idea how to solve it ?

Saturday 4-Nov-2006

... by: Cargill, Czech Rep.

Load Sudoku:

This is partly solved sudoku, that crashes X-Wing strategy and doesn't get solved by the solver (had to disable X-Wing to proceed further).
However it has only one solution.

Andrew Stuart writes (6-Nov-2006):

Hi Cargill. It was slow but didn't hang for me. I've restarted IIS and it seems to be a bit faster now.

Friday 3-Nov-2006

... by: Pompeo M. ACQUESTA, Italy

Load Sudoku:

Many Thanks for your beautiful sudoku solver and your explanations: It help me day by day.
I dont understand why in this sudoku

HIDDEN UNIQUE RECTANGLE removing 9 at J7 because of GJ17 and two strong links on 3

Thanks very much


Pompeo M. ACQUESTA

Roma
Italia

Andrew Stuart writes (6-Nov-2006):

ok, well the short answer is


If any four cells contain a pair X/Y and three contain additional candidates, then one of X or Y can be eliminated from the cell diagonally opposite the bi-value cell if the other candidate in the pair forms two strong links along the row and column.


But I really need to expand and supply examples. It is in the forthcoming book, however!

Wednesday 1-Nov-2006

... by: bente, My

Hi Andrew,

Your solver is a fantastic trainer - actually! A great bulk of the hard-to-understand theories and technique are clearly demonstrated and explained by your solver. Yours is the best so far. It certainly helps me to progress tremendously. Thanks.

bente

Andrew Stuart writes (6-Nov-2006):

Thanks Bente!


General message for posters here: sorry I've not been around to respond last two weeks. Lots of good questions here. It will happen!


Andrew Stuart

Tuesday 31-Oct-2006

... by: Randy, Portland, Oregon USA

Absolutely love the Solver. Thank you. Could you work on a Sudoko Monster Solver? I would love to do them if I could print out the candidates; otherwise, it's way too time consuming just to set up to solve.
Please consider and thank you again.

Andrew Stuart writes (6-Nov-2006):

Hi Randy, yes if by Monster you mean 16x16. I have a prototype, one with only the basic strategies. In the job queue to put on the site.

Sunday 29-Oct-2006

... by: Territan, Glen Burnie, MD

Load Sudoku:

This is a computer-generated sudoku, partially solved by your solver. I'm posting a partially solved one because shortly after this point, the solver goes up to #15 (twice; the first time is very straightforward) and performs a test that seems to go far beyond anything that's shown in the documentation. Hidden unique rectangle? Two strong links? Shto?

Could this be the example of the type 3 unique rectangle that you've been looking for? Or did the solver just do something really unaccountably weird?

Andrew Stuart writes (6-Nov-2006):

Hi Territan, I've found out what the Type 3 Unique Rectangle is and will be adding it soon. See above for the Hidden Unique Rectangle

Saturday 28-Oct-2006

... by: raleigh, USA

Love the sudoku solver. Its fast, easy to use, has great tips and explanations, and its MUCH more powerful than my previous favorite site!

Andrew Stuart writes (6-Nov-2006):

Thanks!

Wednesday 25-Oct-2006

... by: Ray, Rancho Cordova, CA, USA

Load Sudoku:

I derived this puzzle by entering numbers at random until I had a puzzle that tested to have only 1 solution. I then solved it and was surprized at the difficulty of it. I used nothing more sophisticated than a couple of hidden/naked pairs in my solution. Then I let Sudoku Solver do it and was surprized at the apparent difficulty level and the sophisticated tools used. It did not use any of the hidden pairs that I used in my solution.
I'm new to sudoku and I am very impressed with your solver.
I have difficulty identifying hidden pairs when I see 3 or 4 sets of the pair values I want to use. How do you know which ones are bogus??

Andrew Stuart writes (6-Nov-2006):

Hi Rancho


Well done. You made what I'd grade as a Tough sudoku. Excellent!

Sunday 22-Oct-2006

... by: Leonard Trochez, Gretna, La

Thanks for this builder. It's the best I've come across.

My question is : how do I print the Printable version?
I don't see a Print switch.

Thanks

Andrew Stuart writes (6-Nov-2006):

Hi Leonard

Sorry for taking so long to reply. If you don't have a printer icon on your browser menu then [CTRL]+[p] will do the job

Thursday 19-Oct-2006

... by: Sami, Lebanon

Hi,
If I do step by step for the example "Riddle of Sho" it doesn't arrive at the final solution!

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