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 14-Oct-2006

... by: Alok, USA

I am unable to reproduce the bug I reported in my previous posting, so ignore it. I am sure I saw it once but now your solver reports correctly that there is no solution.

Saturday 14-Oct-2006

... by: Alok, USA

Load Sudoku:

This particular example of sudoku does not lead to any solution. However, if I try to find all possible solutions for this problem, your solver takes long time and returns one solution which is not correct at all. Please, look at this example.

Otherwise, your solver is amazing. I had wrote one solver myself and was happy to writer such solver. However, your solver is far better and uses amazing strategies. I will work on improving mine. :) I am waiting for description of more strategies on your website.

Andrew Stuart writes:
This sort of string with so many unknowns kinda hangs the solution count. I'll try and find out why. It should abort once 500 have been reached. That my off-line version tells me there is 1 and the solver says there is an error means something odd.

Saturday 7-Oct-2006

... by: LegalAlien,

This is a really great solver, especially since all steps are detailed and can be seen. have you ever thought of adding an "Sodoku X" (Sodoku with addition of the 2 diagonals, so that these also must contain all numbers) variant to it?

Andrew Stuart writes:
Yes, I'd really like to add more variants. I'm working on Jigsaw and Killer solvers first, though.


Saturday 30-Sep-2006

... by: Charles McCarthy, USA

I was using your program to see qhere I had gone wrong in a puzzle. I entered the initial puzzle, then asked the program to show possibles. I noticed that some of the possibles entries were in fact not possible, because of some deeper reason. So I tried to delete the impossibles. I managed to click on an impossible; it highlighted, the whole array turned a different color (some sort of creamy beigeish orange) , and then I pressed the delete key. Nothing happened. So then I tried the backspace key. The backspace key caused your screen to abort and closed my browser. This last is the bug I wish to report.

I'm running Ubuntu Linux 5.something, P2 400 Mhz, 500M ram, Browser = Foxfire. Java works fine eventually but latency is terrible. A download version would be welcome.


Andrew Stuart writes:
I'll try that sequence myself.

If you want to edit the candidates you need to pick the radio button "Candidates can be Edited or Highlighted" and pick "Edited". Otherwise it will highlight all cells with the numbers in the cell you clicked on.

I would leave the tick box "Show Candidates" on - you needed to see them. I think you needed to click on "Take Step".

I'm not sure how backspace can close your browser. I think your browser would interpret that as a navigation command and go back to the previous page in your history.

Lastly, I closed the site for a few minutes just a short while ago to update the solver with some new stuff. I hope I didn't catch you out while you were trying to use it.

Feedback always appreciated. I know the drawing is not exactly fast in Firefox and I don't have linex to test which is a shame, but I'm pretty sure the javascript is sound. I test it on the windoze version of Firefox.

Download version coming as soon as I can bundle some addition (useful) features into it.

Sunday 24-Sep-2006

... by: DoloresB, USA

I have found your solver very helpful. However, whenever I go back a step, it goes several steps back. For instance, a solved number disapears. I use Safari on a Mac.

Also, I am a fairly new player and I am confused by the advanced methods. With say the Y wing or the colored squares. If you are looking for "2"s say, but the board has lots of them, how do you choose which ones to use?

I read the explanations, and saw it demonstrated on a puzzle I was working on.

Friday 22-Sep-2006

... by: PaulyPitts, New Jersey, USA

This is a response to Paul Akehurst de Visme's (Portugal) question about saving an unfinished puzzle for later use. You can save the puzzle as a favorite in the browser you are using. Select a distinctive name for the puzzle. Later, to recall the puzzle, launch your browser and click on favorites. Then find the puzzle under the name you selected and open it. Your puzzle will be presented as you left it.

As an alternate this, you can email the puzzle to yourself. Later open the email and click on the link. Your puzzle is back again.

Friday 22-Sep-2006

... by: Michael J., USA


What is the time frame for completion of the new solver?

Thank You for all of your hard work on this project.

Andrew Stuart writes:
Sorry I missed this earlier. I've sooo much on my plate, but hopefully this autumn (fall).

Wednesday 20-Sep-2006

... by: Phil, Toronto, Canada

In Firefox, the back step button jumps back 4 or 5 steps instead of just one step.

Wednesday 20-Sep-2006

... by: Michael,

What's the difference between Singles Chain Types 1 & 2? I can't find a reference to it in the strategies.

Tuesday 19-Sep-2006

... by: Alan W., Texas, USA

Hi Andrew,

I surfed into your sudoku page today, and I am very impressed -- it's the best sudoku page I've ever seen on the internet. Thank you for all your time and energy in putting this together and making it available! It's excellent! Keep up the great work!!

Andrew Stuart writes:
Hi Alan

It doesn't have a solution that my strategies can solve. It's a riddle. Google it and you'll see the discussion threads. Very interesting puzzle
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Thank-you everyone for all your questions and contributions.