Solver App for Android
Strategies for Popular Number Puzzles
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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. I'm also directing Str8ts feedback here. Please feel free to drop me a note on the side of the page. Or you can email me directly at .

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

Saturday 19-May-2007

... by: barryn, Massachusetts,USA

Do you know of any websites producing daily games utilizing "tough" or advanced solutions. Most of the games labeled tough or very hard, etc, really aren't that at all.



Andrew Stuart writes:
Have you seen my extreme sudokus?

They all have a known logical solution but the steps require a great number of advanced strategies

Thursday 10-May-2007

... by: ccnorm, california

this is the best site for any sudoku information and help in puzzle-solving. keep up the great work!!

Sunday 6-May-2007

... by: uropian,

Nor can Mehtap! I want to say that your site better throughout the World Wide Web :)
Thank you. Keep it.

Tuesday 10-Apr-2007

... by: Peter Karsanow, United States

Load Sudoku:

Weekly Extreme Jigsaw for Apr 8 to Apr 14 at
Cyndie shape
After a lot of steps, H5 and J6 in box 8 are both 69. The solver skips over "Naked Pairs/Triples" and instead finds a Hidden Pair in column 5 that has the same effect of removing 6 from G5. Strange.
Unless I goofed up on the data entry though, your blocker isn't working on this!

Andrew Stuart writes:
Have another go with this one, it took an hour to debug but I found the problem. It was not looking at the last two boxes for naked Pairs - which is a bit of a howler, but I am very glad you sent in the example and helped me find the problem. Doesn't effect the grade or difficulty of the puzzle since this was created and graded using my offline C++ program and the bug is purely in the javascript on the page. Nor does it speed up the solve steps a great deal for this extreme, but I'm sure it will improve a few other puzzles, so a big thanks indeed.

Saturday 7-Apr-2007

... by:, Port Charlotte, Florida

1st, your "helper" is fantastic. I type in a sudoku from the local paper, check the number of solutions to make sure there is only one, hit the step button and print out two copies of the printable version and work on it at my leisure. my only proplem is how to save and bring back the typed in version. when I save the typed in version to a file and try to open it I get the default version. What am I doing wrong?

So far as any sgestions, I wish thye curser would move to the next square each time a number is entered.

But this is a minor point. Your solver is a godsend for people like me with weak memories


Alligator Jack -- AKA "AJ" by his great Grandchildren

Andrew Stuart writes:
Currently there is only one save option - the save button - which saves the board (but not any notes or candidates) as a cookie - you can use re-load to get it back. If you return to the page any other way the example sudoku loads. If you want to keep many puzzles I suggest you enter them and use the email button. That gives you the important 81 number string which you can save to a text file. You can copy and paste this back into the solver using the import button

I am working on an off-line version which is much better as keeping many sudoku puzzles in a history and saving them. Hopefully ready in a month or so

Friday 6-Apr-2007

... by: Paul Helbig, California, USA

What is the block you've installed on the solver. I use the solver to show the methods you use to solve a puzzle when I reach a "dead end".

The solver has helped me learn methods to solve many difficult puzzles.



Andrew Stuart writes:
Paul, the blocker detects when the puzzle being solved matches either the Daily Sudoku or the Weekly Extreme Sudoku competition puzzle on the site. The block is in effect until the competition submission deadline passes.

The idea is to prevent solvers from using the solver during the competition. You will get a warning message if your puzzle is blocked, and solving stops. If you don't get a warning, the solver works normally.

Saturday 31-Mar-2007

... by: Greg, California

Load Sudoku:

The above Sudoko, posted in San Jose Mercury News on 3/30/07, does not solve with your page. The program clears out the easy ones, then trys X-Wing and just shows "wait". Not sure what is going on. The CPU is not being used much, and I can exit the routine with the back button. Anyway, thought you would like to know.

Greg Buchanan

Andrew Stuart writes:
Greg, when the solver shows "wait," it has sent the puzzle to the server, which executes a program written in C language to run the advanced strategies. Occasionally, internet congestion may prevent the server from getting back with a result, and the web page gets stuck with "wait."

To get around the problem, always save your puzzle with the Save button. You can Save just befor the solver runs an advanced strategy. Close the solver page when the error occurs. Navigate from a fresh browser window to the solver page and then click the Re-Load button on the page. Click take step and, hopefully, you will get results this time around.

Your puzzle did solve when I tried it.

The solver can also appear to get stuck on "wait" if you have given it a bad puzzle. Results may be returned and shown, but the "wait" doesn't go away.

Thursday 29-Mar-2007

... by: Donna T, Texas

Great web site. It has helped me solve many suduko puzzles.

Wednesday 21-Mar-2007

... by: jonnyfolk, France

Thanks for your site. I usually make my way here after staring blankly at a puzzle for 40 minutes or so. Often, I'm ashamed to say, to be told that there's something quite straightforward I'm overlooking, which is very annoying of you!

I'm using a macbookpro with core2duo and running Safari and I find the solver to work very on this set up. I thought you might like to know that...


Andrew Stuart writes:
Thanks for your input, Jon!

Tuesday 13-Mar-2007

... by: Gultekin KOMANLI, Istanbul

Great site to learn strategies for solving! Thanks a lot.

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Thank-you everyone for all your questions and contributions.