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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.

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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!

Thursday 13-Oct-2022

... by: Brian Mottershead, United States

Thank you. I am looking forward to trying some of the "classic" ones.

Monday 10-Oct-2022

... by: Maarten, The Netherlands

Hello,

First of all, I learned a lot of sudoku through your website, so thank you a lot! I was able to create my own solver and creator of puzzles thanks to your explanation of the different strategies.

In https://www.sudokuwiki.org/Sudoku_Creation_and_Grading.pdf you mention that you use a brute force method to see if there is a single solution while you are creating puzzles. Why don't you use the solving strategies for it? Is it because of performance reasons?

Kind regards,

Maarten van den Hoek

Andrew Stuart writes:
Sorry for the late reply. Did you see this article? Goes into some of this. Happy to answer follow ups

Wednesday 5-Oct-2022

... by: Brian Mottershead, United States

Hi,

I love the site. Thanks so much for doing it.

On the web, I often run into references or links to the David FIlmer Unsolvables, usually in the context of a discussion of what is the "hardest" sudoku". For example "David Filmer Unsolvable #28" is often mentioned as the hardest sudoku. Another contender for "hardest" is #49.

However, if there is a link (generally in the form https://sudokuwiki.org/Weekly_Sudoku.asp?puz=49,) it does go to the "Weekly Unsolvable" page, but only showing what is ever the current Weekly Unsolvable. Today, thae link for puz=49, shows number 516.

In the "archive" pulldown on the page. various previous numbers are listed, but not older ones. For example, right now, you can only look at numbers 477 to 516.

I am guessing that at some point, you changed this page so that the archive only shows the most recent 40, Or perhaps #28 and #49 are in the current archive, but the numbering has changed.

In any case, would there be a way to bring back the "classic" David FIlmer Unsolvables, with the old numbers, so that the old links work?

Best regards,

Brian Mottershead

Andrew Stuart writes:
Yes eventually I'd like to include them all as some sort or premium service but that's way down the line.
However I like your idea so I've added David Filmers ones where they were in the series 1 to 200

Refresh the page and check the list

Thursday 16-Jun-2022

... by: ROY WATTS, USA

I thought I could enter it prior to entering a puzzle but alas, I was wrong. Would it be possible to get it added to your site. I am very much interested in creating jigsaw puzzles and rely heavily on your solvers to insure they work. This particular shape gives new life to leftovers! Excellent site, btw.

Andrew Stuart writes:
I like your pattern and I've added it to the Jigsaw solver. Last in the list. You need to give me a name for it ;)

I've included four examples. I've not run the generator for very long so the first three are rather vanilla. Number 4 is an extreme.

If you don’t see the new pattern used [CRTL]+[F5] to reload the page

It's a long standing job of mine to reorder the solver to allow user-defined maps. I really must get on with that some day

Monday 30-May-2022

... by: James McGinn, Ireland

May 22 puzzle packs are listed as May 20

Andrew Stuart writes:
Fixed! Thank you

Friday 27-May-2022

... by: Reuben, BC

Hey Andrew -
I met Jeff years ago and he introduced me to str8ts. I still play every day. I had a novel idea that I thought you might want to consider. When someone plays they could toggle on or off the option to see how their solution time compares to the times of others. I'm constantly competing against myself, but it would be fun to have the option of seeing how fast others are completing the puzzles.

Cheers,
Reuben

Andrew Stuart writes:
Yes, I'd like to introduce more competitive components like that. Relatively difficult tech however, all that asynchronous communication. Somehow need to make a little more money from the site to feed that sort of development. Mainly that's the pinch at the moment.

Friday 20-May-2022

... by: Stratos, Greece

Dear Andrew
I am using your sudoku solver for many years and helped me a lot. SO many thanks for that and congrats for your job. However I have a question for you. I am a poor human solver. What I see is that all those Diabolical, Extreme strategies and even many of the Tough ones, can only be used by a computer. I can only use some of the simpler Tough's like X-Wing for instance, but nothing more. Do you really believe that a human being is able of using strategies like Jellyfish, Fireworks, Exocet, etc. without using a computer ??
I am just curious if my mind's capabilities are small and if there are genius people who can use by heart all those strategies you have invented.
I would really appreciate your answer.
Many thanks in advance
Stratos

Andrew Stuart writes:
It is true all strategies are easy for computers - if you can code them right - which is the fun part for me and other programmers. I was interested in exploring this area and seeing what crazy stuff could prove useful. My big divide is between "pattern" based strategies and "trial and error" - whether there is a logic based on the state of play or whether some puzzles need a plug-and-test approach. Humans use that but I find trial and error unsatisfying since it doesn't tell you "why". So for most people the most complex strategies are not really for humans. That said, someone had to invent them and they came out of thinking about a problem, not asking a computer to find a strategy. Maybe an AI can go meta and think up strategies but I don’t know how to set that up. So some people - at least the inventors - were mentally exploring these spaces. And I do know some people will pen-and-paper complex chaining, but I don’t and most don't and they still crack them. I can't duplicate human intuition. Also, I would never torture an audience in a newspaper with an extreme and I believe my puzzles are harder than most. Diabolicals are my commercial maximum.

Friday 13-May-2022

... by: James Leonard, USA

The archived Sunday puzzles for May 01 and May 08 are blank and the date shown for them is December 30 1899 ! Cheers.

Andrew Stuart writes:
Thanks for the alert. Looks like I uploaded new stock for all the grades except the Sunday extremes. I've put them up now, have a look

Appreciated!

Sunday 8-May-2022

... by: David Andrew, England

It's happened again! Just like last Sunday, the Extreme Daily Sudoku is blank. I have Javascript enabled on my Mac, and the other puzzles, including the Extremes for April and before, are all fine.

Andrew Stuart writes:
I've put them up now, have a look. Sorry about the delay!
Cheers

Saturday 1-Jan-2022

... by: Jeff Sussman, new sudoku user

Love your work. Very helpful. Have yet to find one you can't handle.
Q: Can a user paste an entire Sudoku directly into the small board?
(I'm keeping a list of them in Excel with comments and it'd be great if I can copy/paste back into the small board later.)

Andrew Stuart writes:
Not in a 9x9 square shape, no. I can see the utility of that, but if you are working in excel, should be easy to concatenate the numbers into a cell so they are all in a line. You can even add the prefix

https://www.sudokuwiki.org/sudoku.htm?bd=

to the start of the cell to get a direct link from excel to the solver
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2015 2014 2013 2012 2011 2010 2009 2008 2007 2006
Thank-you everyone for all your questions and contributions.