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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 22-Dec-2022

... by: Stephen, UK

Str8ts Re-Start button is not resetting the grid.
I get the dialogue box asking to confirm to clear, but the grid retains my entries.
Using Firefox 108.0.1

Andrew Stuart writes:
Hi Stephen. No email to reply directly to but I think you were using a version I corrected about an hour later. [CRTL]+[F5]

Thursday 22-Dec-2022

... by: Rudik49, Germany

I've noticed today (22 dec 2022) that it is no longer possible to start solving the str8s puzzle on the screen and - once you get stuck - print it out with the numbers already filled in. Only the original blank puzzle - without my solution - is printed out, so I have to start from scratch again. This must be a recent change, because I believe I could do it a week ago or so. Can this be changed back to how it was before? Actually, it always worked this way for the daily puzzles (1 to 4 stars), not for the weekly extreme str8ts (5 stars).
Regards, Rudi

Andrew Stuart writes:
Good catch. I'll put that functionality back. Not sure every player had it but I think the new ones should

Thursday 22-Dec-2022

... by: Hanns, germany

Dear Andrew ,
I still use the german str8ts and now some links are not working.
This is f.e. https://www.str8ts.com/newplayer/Print_Str8ts.asp?lang=de&a=7784
which is used for the printable version. If you would like to give me a hint for a workaround.
best regards Hanns

Andrew Stuart writes:
I'm breaking a lot of things as I reorganize and upgrade the sites.
Trying not to! but it happens.
Really appreciate your alert, fixed the problem now
Any more, do share

Wednesday 21-Dec-2022

... by: JustMe, E

New design is unplayable on iPhone: too many trial numbers in one or more columns may shrink other columns beyond selectability

Andrew Stuart writes:
ok will look at this. bug if the columns are changing

Sunday 11-Dec-2022

... by: phil, USA

I can't get todays Killer to come up in a Print window. It says "Bad Link". I miss it.

Andrew Stuart writes:
Thanks for the warning. Been up and down all day as I figure out a new error handler. Should be good now

Saturday 10-Dec-2022

... by: Cynthia, San Francisco

I got the following when trying to Take Step for hint. Why does it men?
" Server Error in '/' Application.

Andrew Stuart writes:
Yeah should be sorted now.

Thursday 1-Dec-2022

... by: Palaquai, USA

Feedback/comment
This site is the very best resource I've seen for understanding the most advanced solving techniques! Thank You, I've learned a lot from this site...

Palaquai

Andrew Stuart writes:
Thank-you!

Friday 18-Nov-2022

... by: puzzler311, United States

Load Sudoku:

Just curious if the "Platinum Blonde" is in your coffers of unsolvables and where it might rank.

Andrew Stuart writes:
Not seen this before. Where is it from?

Wednesday 26-Oct-2022

... by: Michael Hayes, Florida

I notice that in your Sudoku solver, for some tests, e.g. Hidden Singles, you will find as many as exist from searching all the rows columns and boxes, before returning to 'check for solved cells'. Yet, for other tests, e.g. NakedQuad, after finding one, you will return immediately to 'check for solved cell'. In your example for NakedQuad, after removing the 1/5/6/8 bits in Box 1, there is now another Naked Quad, 1/3/7/9 in the row B - in fact there several more, e.g. 2/5/6/8 in column 2, 1/4/5/9 in Row A. My question is, why not continue to search all the rows, columns and boxes for a particular test vs immediately returning to 'check for solved'? I'm guessing it's because when you discovered the NakedQuad in Box 1, you had already done your search of the Row and Column blocks, and you only search each block once for a particular test, rather than say, in a while loop until no more are found.

Second question: Is there any reason to search blocks in any particular order, e.g. boxes first, then rows, then columns?

Andrew Stuart writes:
Good questions. For the very easiest searches it would be too tedious to only return them one at a time. Often it's a question of balancing information displayed versus how much to click. For almost all other strategies it is necessary to return the first (or best) since it would be a muddle to display two or more. Also there can be knock on effects that might solve the puzzle if the same strategy is allowed to recurse and be exhaustive and then the user wouldn't know what had happened. Some strategies such as the chaining ones do search for all instances, store them in a list and sort them by some rules to get the "best". In a future version I'd like to allow the user to cycle through them.

Searching is 1 to 9, top left to bottom right. Mostly this does not matter as can be shown by rotating the puzzle, but sometimes can. Not a lot of choice when proceeding linearly and thoroughtly.

Sunday 23-Oct-2022

... by: Michael Becher, Germany / Munich

Load Sudoku:

Hi Andrew,

yer nice page and solver. Hard to find some sudokus where your solver does not find a solution...
I have attached one.

Best regards
Michael

Andrew Stuart writes:
Good one. Where from?
The candidate density is high. That's a sign of difficult or unsolvable.
Page:2024 2023 2022 :1 2 3 :2021 2020 2019 2018 2017
2015 2014 2013 2012 2011 2010 2009 2008 2007 2006
Thank-you everyone for all your questions and contributions.