... by: PaulyPitts, New Jersey, USA

Would it be possible to add a button that would yield the instant puzzle solution ready for printout? While I'm working on a puzzle, like to verify my individual square solutions to check on my work. I also find this very instructive because it gives me instant feedback if my logic is faulty. If there was one button to click that would present the solved puzzle for printing, it would be of great help.

By the way, your Sudoku site is the very best. It just keeps on getting better and better. Keep up the good work.

PaulyPitts
Andrew Stuart writes (24-Sep-2008):
I don't plan to add an "Instant Solution" button. However, click "Solution Count" and copy the solution string. Open a second solver window and click Import a Sudoku. Paste the string and click OK. Click either the Print 1 or Print 2 button and then print the page with the solution. Lastly, thanks for the compliment!

... by: pjf, Ontario, Canada

Load Sudoku: 008000109000605007006070200001700054000409000270006000009060800400503000103000500

I think you are missing a easy strategy

Consider 2 pairs; not in a box and not on any on any line.
Those 2 pair define a square.
The other two corners of the square cannot contain any
possibilities of members of the pair.
Andrew Stuart writes (3-Sep-2008):

That's an interesting observation but I don't think it is always true as a general principle. I've picked a random diabolical to look for an example:

D1 and E9 is the pair. E1 contains a 6/8 as well. It forms a short Remote Pair chain and E1 must contain a 6 or 8 as they are the only candidates left. Our pair must contain the same number (either 6 or 8).

So while both opposite corners of the pair cannot contain BOTH numbers they can contain ONE of the numbers - which one though cannot be determined without other strategies.

... by: Arne Hajonides, Wilnis, Netherlands

Load Sudoku: 040027003060004007102006000004050300210700000000003090507000000000060000001900502

Hello Andrew

To start with, this is great site.

I have a question about "single's chains, type 1". I'm trying to solve the above puzzle, but I don't understand why the 8 is removed from D9 and not from the another of the cells in the chain (D2, G2, H3, H9)?

With another words, if I start the chain at D9->H9->H3->G2->D2, why is not the 8 removed from D2? (D2 = 8 in the solution and the solution count = 1)

Arne

ps. The puzzle is from a Sudoku-book
Andrew Stuart writes (18-Aug-2008):
Do have a look at http://www.scanraid.com/Singles_Chains Which explains it more fully, but your example is a nice clear one. Either the two YELLOW cells will be the solution or the two BROWN cells will be. We don't know which was round. But that means any 8 that can see both colors can't be a solution. It can be removed. Type 1 works off the chain.

... by: Bernard Skehan, USA

This is the very best site on sudoku. It is better than any of the published books. I hope that someday you put all this in a book form, which would help when studying the strategies.

Please keep up this site, it is invaluable to beginners and advanced players.
Andrew Stuart writes (18-Aug-2008):
Thanks Bernard!

... by: Doug, Hong Kng

Your site is great. Have you produced a solver for the sudoku puzzles where the diagonals also have 1 -9 in them?
Andrew Stuart writes (30-Jun-2008):
Yes I do have such a solver. Take a look at http://www.sudokuwiki.org/SudokuX.htm

... by: Dabas, Australia

Your explanations are great!
The section on X-Cycles has been a great eye-opener and I keep finding ways of using these strategies!

Thanks for an excellent site

... by: Judy, USA

Hello,

Thank you for your solver. It has been a great way for me to learn to do the more advanced boards. The clear instructions for each technique are the most clear I have found. I do have a question/comment. Why is the last row labeled J in your solver instead of I? This lead to a bit of confusion for me as I tried to follow the notes for each step. Please note this odd row labeling on the page if there is a reason for it.

Thank you for the great work.
Judy
Andrew Stuart writes (1-Jun-2008):
The reason for that convention is because "I" can look like "1", which can be confusing when talking about cell I1 etc, J1 is simply visibly easier. You should not find "I" turning up in any output from the solver or in any of the documentation

... by: est, usa

This morning there was no PRINTABLE version of the puzzle available, which I have always used to enlarge the puzzle. Please put it back.
Andrew Stuart writes (27-May-2008):
Hi, there was an issue on Sunday/Monday in Firefox. Firefox is case-senstive to html element names and I introduced a bug when cleaning up the code. Fixed pretty quickly and printable versions are working in both browsers today. Do have another go

... by: J McKee, Virginia, USA

Great site! Especially for a non-mensa like me. I have a question about your example puzzle for Sashimi Finned X-Wings. Would not the 4 in D2 have to be absent for this to work? I'm assuming that the fin is the only allowable 4 candidate deviation in the X-wing rows. If the 4 in D2 is actually not a problem, could not E6 and F6 just as easily be considered a fin? Straighten me out, please.

Thanks!
Andrew Stuart writes (8-May-2008):
Really glad you wrote in since there was a problem with my diagram. Not sure how but the screen snap shot I took was of a position a few steps before the correct situation. Have a look at the page now. Even I was struggling to make sense of the example because there were stray 4s in D2 and D3. But having removed them it makes sense now. So, correct, the 4s in D2 and D3 do have to be absent for it to work. These are recent pages, and I suffer "wood from the trees" syndrome when I check what I write and do. Appreciated

... by: Relaymsn, United States

Great site. I was looking for a site for solving some unsolvable (to me) Sudokus that I had accumulated. Some of the techniques will take me a while to do with pencil and paper but I can master others quickly.

By the way, the site worked great on Safari 3.1.1.
Andrew Stuart writes (4-May-2008):
Thanks for the feedback - appreciated. And good to know its works on Safari as well!

... by: Rajk, Netherlands

Escargot
Escargot does not have a solution?
Run out of known strategies.
Andrew Stuart writes (3-May-2008):
Yep. That is a semi-famous sudoku invented by a Finnish mathematician who claims it is the hardest sudoku ever. Currently aboyt 0.2% of randomly produced sudokus can't be solved with my logical strategy set so there is plenty of work still to do...