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!

Sunday 10-Dec-2006

... by: Des Fry, UK

Something has changed with printing, maybe because I have upgraded to Firefox Version 2 web browser.
When selecting printable version, it displays on the screen as before but when printed the entire grid is printed smaller but with numbers the same size. The result is that there is very little white space left on the paper to write new numbers in.
On A4 paper the grid is printed 4.5 inches square (11.5 cm). It used to print 6.5 inches square.
Just tried it with Internet Explorer V7 - prints correctly (as FireFox did before). Drat! - I like Firefox.
Thanks for a great product!!
Regards - Des

Andrew Stuart writes:
I only have Firefox - seems to work OK. I'll try and get v2.

Saturday 9-Dec-2006

... by: Larry COoper,

Sunday 3-Dec-2006

... by: Al, USA

Something has broken in the program. As soon as it jumps into the second group of solutions, it finds the first solution in that group (according to the dialog), then hangs on the first strategy (X-Wing).

Great program by the way!

Andrew Stuart writes:
Should be working fine. 2nd December I make an important update (v1.39) to speed up advanced strats. This means some browsers will not be in synch. If you clear your cache and re-fresh it should work again.

Saturday 2-Dec-2006

... by: EJC, United States

Will your Puzzle Solver be available for downloading onto our personal PCs so that we could work offline? If so, when? I have purchased Michael Mepham's program; it's great, but doesn't appear to readily handle Jigsaw Sudoku puzzles. Thanks!

Tuesday 28-Nov-2006

... by: Gordon, Valle Crucis, NC USA

Subject: Daily Jigsaw Sudoku Number 386, Diabolical using the Form called STRIPES by Leo Binkowski, IL, USA.

Problem: Program hung (wait state) on pointing pairs.

I had entered the original numbers into the form and saved it. What I had so far in my solution as far as I got matched up with yours. But you went on to some Extreme Strategies (like Death Blossom) that were eliminating possibilities but not adding any numbers before it hung.

When it hung I attempted to go back a step but the "Take Step" went gray. I took note that B6 and H6 contained 45 and many of the boxes contained 5's. I reloaded the form and added a 5 in B6. I call this the WAG strategy. It worked.

You have created a great learning took. Thanks.

Gordon Brazas

Andrew Stuart writes:
I've had reports that most people in the UK - where the server is - find the advanced strategies pretty quick - but out here in Mexico - where I am, they can take some seconds or more and I've had it hang as well. I think it is shear numbers. If this carries on I'll have to find an alternative method. I do have an active x control that would run the harder strats on the client - which would be pretty fast.

Monday 27-Nov-2006

... by: Sandy, US

The method I use to "cut to the quick" on solving is as following:
I first x-hatch looking for 2 or 3 numbers that go in a box but in a row or a column there. (In other words, they must be adjacent!) These digits I underline signifying to me they are blockers for the box, column/row.
2nd I x-hatch again just to pick up new ones.
THEN I proceed with the usual by putting in all the possibles, ckecking then the other strategies as singles, doubles, etc etc. etc.
RESULT of marking all these blockers is firstly utilizing these as if they were single digits, blocking a col/row and giving more information to solve many cells in the original x-hatching.

Please do try this and perhaps you can explain it better to others.
(THO it is probably already known but I would think more people would do it as the first two steps.)

Any comments?

PS I am in AWE of your solver. I find it a most useful learning tool!!!!!!

Andrew Stuart writes:
Hi Sandy, looks like you've really thought about this. Nice to see some new strategies, thanks for sharing. Do post on the forums, eg at

Monday 27-Nov-2006

... by: Cesar Campo, Colombia

Excellent solver and it really helps understand all the strategies with the explanations provided.
I would only suggest an enhancement when importing Jigsaw puzzles since there are countless number of shapes, especially ugly shapes, it would be important to also have the opportunity to import the shape itself if the shape is not in the list you have, that way you can use the solver to solve any Jigsaw Sudoku no matter what shape it is.
I've created some beautiful shapes myself, they're probably also published somewhere since there are thousands of people creating Jigsaws shapes at the same time though.
Thanks and congratulations for the excellent Sudoku solver.
Cesar Campo

Andrew Stuart writes:
Yes, I'd like allow other shapes. The problem is designing a shape making page and allowing people to keep the shapes somehow - so the page doesn't loose them. Definitely something I'd like to add.

Sunday 26-Nov-2006

... by: Tawitko, Black Forest, Germany

Hello Andrew,

many thanks for this helpful site. I'm well impressed by the amount of the different solution strategies, you have implemented.

And now there is even the solver for Jigsaw puzzles, wow.

Recently I found a different shape (like a red cross), link for example pic:
This puzzle was posted in

Best Regards

Andrew Stuart writes:
That's a pretty shape. I'll try and add it to the list, Thanks!

You can read German, yes? Does the page say if that jigsaw shape has a name, or a creator. If I add it to the list I'd like to credit the person or web site who made the shape. Probably a long shot, but I thought I'd ask.

Sunday 26-Nov-2006

... by: bente, my

Another great piece of sudoku treasure by Andrew Stuart! Most instructive guide, a great teaching aid. I went through with it on a diabolical jigsaw and it worked perfecctly. I benefited from it immensely. Thanks Andrew.

Andrew Stuart writes:
You are most kind, cheers!

Sunday 26-Nov-2006

... by: Michael J., USA

Hello Andrew,

I don't know if this is a bug or if I am missing something.

Using the first example in the Jigsaw solver, I took a step then went to printable version and printed it.

The canidates on the printable version show "3568" in box A2, but the printed version shows "003056080", this is true across the entire puzzle.

I am using Windows XP SP2 and IE 7

Thank You for all your hard work on this site!

Best Regards


Andrew Stuart writes:
Thanks for the report. I've not tested in IE7 yet. There are zeros in the printable version but they should be white and not show up. They are there for padding and positioning only.

OK, I've removed the zeros, I was getting grey zeros on prints. Not so perfectly lined up now but pretty good.

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Thank-you everyone for all your questions and contributions.