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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 .


Post a Comment or Question here...
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Any Sudoku you want to publish here for easy loading into the solver - 81 characters, use '.' or '0' for unknowns.

public - comment/question will be added to feedback column
private - email comment/question directly to Andrew Stuart, don't display here

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If you are writing to alert me of a problem (thank-you!) please include a url to the page in question.
Can get fixes in quicker if I know immediately where to go.
Many thanks to all the people who have helped improve the solvers and strategies with their feedback!

Monday 17-Feb-2025

... by: Boris, Croatia

Dear Mr. Stuart,
first I want to praise the quality and scope of the Sudokuwiki, really impressing!

I am retired, so I don't have much idle time and I limit my activity to the basic sudoku, not even the very tough, just moderate ones.

I purchase printed brochures with sudoku puzzles, enter them im your solver to print them and solve on the paper. In last several months I had problems with printing the sudoku with given numbers only, instead of printing empty cells blank, solver fills them with all nine candidates, distorting the cells.

To avoid this problem, I start solving the sudoku on-line as far as I can without writing the candidates, then choose the option "Automatically clear" and repeat the last solved candidate to obtain the real remaining candidates and then print the sudoku with them.

Can you help me with this problem? Why empty cells can't be really empty?

Once again, thank you for running this excellent site!

Kind regrds, Boris Halasz, Zagreb, Croatia

Andrew Stuart writes:
Very glad you are enjoying the site. Yes I've tried to make the print mirror the solver as much as possible. People like to set up candidates and then proceed manually. To print without candidates untick “Shown”
Send me a screen shot of anything distorted. I would love to fix that

Saturday 15-Feb-2025

... by: Yannick, Germany

Thank you so much for your Killer Sudoku Solver, just helped me after I got stuck for an hour while also teaching me something!

Andrew Stuart writes:
Very glad to hear that! Good luck wth your next one ;)

Sunday 9-Feb-2025

... by: John, Virginia

Load Sudoku:

I got stuck on this NYT sudoku so I entered it in your solver. But your solver took some steps and then got stuck looking for naked pairs/triples (it says "wait") and it is no longer possible to take any steps

Andrew Stuart writes:
Give it a go now. Works for me this morning. I am still trying to understand what causes this. Sometimes it is deliberate as when I’m replacing the binary with a new version. Sometimes the server is busy. But I’ve seent go to 100% cpu as well.

Saturday 1-Feb-2025

... by: jdrano, michigan

I love your killer Sudoku solver. I usually make a mistake because of the notes in the small squares I'm working in. I can read the notes because they are clear(better than my handwriting...lol). In general; hands down; this site is best I've worked with.

Andrew Stuart writes:
Many thanks, kind words!

Saturday 25-Jan-2025

... by: Warren Jobs, USA

import a sudoku works once for me if I use paste. when I past another it says only 29 characters entered although there were 81. the first 52 characters in line 1 are ignored. I have tried this in 3 different browsers. same results in all

Andrew Stuart writes:
Can you send me what you are trying to paste in?
Will be formats I have not anticipated.

Saturday 25-Jan-2025

... by: Nada Savatic, US

On the Sudoku solver, there are 2 buttons (Enter new killer or Modify this Killer). Pressing either button takes you to the same interface. The current killer is displayed and if you want to do a new killer, you must press the Start Over button.
Why have 2 buttons? Have one and call it Enter New/Modify this Killer.
Thanks for providing such a great tool.
Nada Savatic

Andrew Stuart writes:
Yes this actually by design. I found it was too easy to lose progress if you accidentally closed the popup or tab and rather than frustrate the user this way, I try and save it and reload it automatically. If you use “modify killer” that will fill the buffer for Work In Progress and be show when you “enter new killer”. Hence [start over]. Maybe I could change the button text if this was filled or pop up a question. Welcome any clearer UX ideas.

Thursday 23-Jan-2025

... by: Pauline, Europe

I cannot print the killer sudoku any more, neither in black and white nor in colour. There seems to be an error in uploading the sudoku to the printing format. Please help!

Andrew Stuart writes:
Found the problem on the Killer Solver page
Please refresh the Killer Sudoku page. Should now work
Daily Killer puzzle should be okay
https://www.sudokuwiki.org/Daily_Killer_Sudoku.aspx
I'm seeing a full board:
https://www.sudokuwiki.org/Players/Print_Daily_Killer.aspx?grade=2
Also use [CRTL]+[F5] in case there is a cache issue

Thursday 23-Jan-2025

... by: Barbara Hill , Near Chicago

Something is wrong with the Sudokuwiki app (Android). I have been unable to download the daily puzzle for the last two days. I just get an error message, and the puzzle list ends on Monday. Thanks for your attention.

Andrew Stuart writes:
Try again now. Did some nudging under the hood

Friday 17-Jan-2025

... by: Phil, UK

Hi

Love the site. Apologies if mentioned before but it would be mega if you could enhance the Killer solver to allow mini "brute force" to complete the solving a puzzle when the solver has run out of logical steps. The technique I have ended up using with your tool is a manual logic tree where from the first point I am forced to make a guess, say for example on a choice of 2 numbers in a cell ... I record that cell and choice made (a number or a pair etc) as a guess node and then continue with logic solving. If another guess required then I create a new guess node beneath the prior one ... and continue to traverse the logic tree, returning to the prior guess node when an error detected and choosing alternate guess. If guess node choice is exhausted, then go to parent guess node. Could you do this?

Andrew Stuart writes:
I don’t know if that’s possible. I could add the solution count stuff which is my brute force code. But that requires a minimum of 17 clues. If you get 17 solved cells you have pretty much busted open the puzzle and it should solve. Most hard killer that the solver cant help with have very few solved cells. I know the killer solver lags behind the Sudoku one (which is 1/30,000 random puzzles) like being only about 50% on the hardest grade. [Save] and [reload] will give you a save point. Then you can enter a single number in a cell and see where it goes.

Tuesday 14-Jan-2025

... by: Sagan, US

The latest glitch I have found is the Arto Inklo Escargot puzzle. It's wrong. It has an extra given digit that doesn't belong there. This would affect solve time, your difficulty calculations, etc., etc.

Andrew Stuart writes:
Seems like I got the puzzle definition from a forum post in 2012 on the most popular Sudoku forum at the time. This included the extra 1 in H3. I don't think it seriously affects the grade or solution path since 1 in H3 solves trivially with a hidden single. But I appreciate the correction and yes embarrassing to have had the extra digit so many years. Refresh the Sudoku.htm and the corrected Escargot will load. Also, I see I did make this correction in the past but not in all places. Will try and find them all.
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Thank-you everyone for all your questions and contributions.