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!

Wednesday 10-Apr-2019

... by: Jimd, Usa

I enjoy using the program when stuck . I would like to enter my sudoku in the left hand box and which automatically goes to the right hand box but then use the right hand box to attempt to solve the sudoku as best I can with the numbers showing before going to “take step” until I have to. How can I use the right hand box to do this ?

Andrew Stuart writes:

Click on "Candidates can be [] edited". Entering a single number will give you a big solved number

Monday 1-Apr-2019

... by: tilrman, USA

Well done and thanks!

Andrew Stuart writes:

Thank you!

Friday 1-Feb-2019

... by: John, UK

Killer Solver hasn't worked on my PC for a few days

Andrew Stuart writes:

Need more info! And an email address so I can write back to you!

Wednesday 30-Jan-2019

... by: orangmerah, Australia

My online (PC) sudoku is constantly throwing up a drop-down box with choices for entry that bear little or no relation to possible solutions. What's more, it often won't allow me to input my own choices - and there's nothing wrong with my keyboard.

Andrew Stuart writes:

Yes that is an annoying feature of modern browsers. I can put a setting in a field to ask it not to, but what page are you on? What website?

Friday 25-Jan-2019

... by: Clark, Michigan

Terrific tool. Thanks.

Wednesday 16-Jan-2019

... by: Camillo J Pasquariello!, USA

I run the solver fine on my Android smartphone , but it will not run on my Android tablet.
Phone is 9.0, tablet is8.0

Andrew Stuart writes:

That's disappointing. Can you give me the model and specs? Especially the screen size and resolution.
There are so many makes, models and android versions it is very difficult to ensure that it works on all devices

Thursday 10-Jan-2019

... by: Lars W, Denmark

Load Sudoku:

I am not really sure if this is a bug or what, but its puzzles me.
It is a Sudoku X which I tried to solve as a std sudoku to make it a bit more challenging. I got as long as the sudoku given above. Then I would try the solver, still the standard (not X).
The solution count says 3. But clicking step the solver is coming up with one unique solution. If fires the BUG rule once to get upper left corner solved to 7
Then there is only one solution straight forward
But if you put 1 or 4 in upper left corner there is also one solution

So solution count is correct, and the BUG rule is somewhat too smart. Or at least it only works correct if solution count is 1

In addition the BUG rule find the only solution if you solve it as a x-sudoku

rgds Lars

Andrew Stuart writes:

Yes the BUG rule is not reliable in Sudoku X and there are less strategies in the list. I have not been able to prove all the normal Sudoku ones for X. Especially Unique Rectangles. Use the wrong solver at your peril, it may produce undesirable results. While a solution may be both a normal Sudoku and a Sudoku X (it fits both) there may be too few clues for a normal Sudoku. Extra constraints = less clues

Sunday 6-Jan-2019

... by: Nigel, E. Sussex. UK.

Hi. An absolutely excellent site, love it. Just solved today's Killer in the Solver. I realised I'd made a mistake and my answers to two of the cages didn't add up to the correct totals. Not picked up by the solver which at the end advised All done. Solver appears to have checked Sudoko rules have been complied with but not that cage totals have been followed. Screenshot available if useful. Nigel.

Andrew Stuart writes:

I'd appreciate an example and screen shot, thanks
Seems like a simple rule - and I'm sure I coded it. However the solver messes with cages a lot, internally, after all the cage splitting and so on. Been awhile since I looked at this part but I'd have to check. Sounds like I should add a check on client side if it's not there
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Thank-you everyone for all your questions and contributions.