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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!

Sunday 23-Mar-2025

... by: Phil Zell, U S

For the last 2 weeks, when i press the key to Print the puzzle all I get is a sheet with the row and column numbers- NO Puzzle. I have to Print the Screen and Paste it in WORD. What happened?
Thanks
Phil Zell

Andrew Stuart writes:
Okay found it. The Daily Killer print. Can you press [CRTL]+F{F5] on the print page to refresh.

Sunday 16-Mar-2025

... by: FHessel, Europe

Followup:
Actually, I just saw, that the puzzle on the main page is ok, it is only the solver, falsely drawing the 'funny shaped box' (I used the word 'cage' before, that was not what I meant).

Andrew Stuart writes:
I was working last night on transporting user progress from kenken and killers from the player to the solver. I think I created a knock on bug with killer jigsaws. The solver was not recognising the jigsaw "shape" and was reverting to shape number 1. Very confusing to you, hence all the disparities. The puzzle is fine. I think I've fixed it now. Reload the player in a new tab (just in case there is a problem and you can still see your progress in the old tab). Will say v2.18. Now try the "send to solver" button
Appreciate the alert!

Monday 10-Mar-2025

... by: pAUL, Its not possible to reach your Main Page - ASPX 500 Error.

Its not possible to reach your Main Page - ASPX 500 Error.

Andrew Stuart writes:
Is this still happening for some people? Please let me know the IP address below so I can run some tests. I know the code area that's failing but not why yet. Right pain.
(3.19.246.111)

Sunday 9-Mar-2025

... by: PAUL DAYNES, NEW ZEALAND

There seems to be a problem printing out The Daily Sudoku. Before, if you clicked on any of the Daily Sudokus, the Print Dialog would automatically open. Now it loads the puzzle into the Solver, where one can click on 'Printable Version'. However, the Printable Version is always the same, that is, the latest puzzle.

Andrew Stuart writes:
I changed the first archive section to load the puzzle into the player. This allows access to all the puzzles for that day, not just the advertised day. From the player you can print any of the 4 (or 5 is Sunday).
The third calendar block sends the daily puzzle to the solver. Maybe there was a script update you didn't get on the 9th. How does it look today? I've tested it just now

Thursday 6-Mar-2025

... by: RedNectar, Australia

On a recent puzzle, (link) the sudoku solver found an XY-Chain that was described as

-3[B8]+6[B8]-6[G8]+7[G8]-7[J9]+9[J9]-9[E9]+1[E9]-1[H9]+3[H9]

I have no idea how to interpret the + and - notation, and am struggling to find where this is explained anywhere on the wiki.

Just a link to the explanation would be great!

TIA
RedNectar

Andrew Stuart writes:
Quite right. I thought there was something somewhere but must have got moved away.
I’ve added a section on this page where chains first show up

Wednesday 5-Mar-2025

... by: Tom, North America

Importing a plaintext puzzle looks to join numbers in adjacent lines together, resulting in an incomplete set. For example, two rows (newline separators) :

1 2 3 ... 13
2 3 1 ...

will result in 1 2 3 ... 132 3 1 ... i.e. the 13 and 2 are concatenated.

Function import_user_sudoku() in Javascript file sudoku4.js replaces newlines and tabs with empty strings:

dstring=dstring.replaceAll('\t','');
dstring=dstring.replaceAll('\n','');

As generic white space characters, I'd like to suggest replacing them with space characters. This would keep the numbers separated for the parser. Might not hurt to add '\r' to the replacement, as well.

https://www.sudokuwiki.org/js/sudoku4.js?v=2.75

Thank you!

Andrew Stuart writes:
Great request, happy to oblige. Refresh the solver page and try now

Tuesday 4-Mar-2025

... by: Kai, Germany

i am not sure about the rules concerning b and bx str8ts, so fe if you have got one black cell in one box , does that mean that either the 1 or the 9 cannot be in the box, or is it possible 1234 and 6789?

best regards

Kai

Andrew Stuart writes:
Could be any number. Depends on the str8ts in the rows and columns. The constraint of 1 to 9 in the box is maximally 1 to 9 but is not a 'straight' itself

Sunday 2-Mar-2025

... by: Jacques Guillot, Mandeville, Louisiana

Thank you for your site - I have had unbelievable joy over years using it.

I might have overlooked it, but does your unique rectangle page have to me one of the most basic use cases? Three bivalue squares xy and one trivalue square xyz, so the trivalue square must be z.

I love unique rectangles, but I think the technique is not respected in some circles, because it is not “pure logic.” Do you have any comments?

Again, tremendous love, gratitude, and respect to you!

Jacques

Andrew Stuart writes:
Good question and thanks for the kind words ;)
Sounds like it would be captured by Type 1
But also sounds like Bi-Value Universal Grave
I disagree with the non-UR people. To be a Sudoku puzzle it must have one solution – otherwise it is a different beast and we’re not playing the same game. If so, let’s use logic

Friday 21-Feb-2025

... by: A random stranger, Earth

Der Mr. Stuart,
I've been enjoying 1 to 25 as of late. However, there are several things which I've noticed which I consider rather unfortunate:
-on mobile in portrait mode there isn't realy a way to go to other places on the site (contrary to this domain, where you can use the page Index link to find your way around)
-The Puzzles don't seem to be ordered in order of difficulty. Today, for example, Puzzles 2-4 solved pretty easy for me, while Puzzles 1 is so far unsolved.
-particularely bad together with the previous point and contrary to e.g. the sudoku player, the player for 1-25 doesn't seem to save partial progress so I can always come back later.
Kind regards, a random stranger

Andrew Stuart writes:
Good points, I will fix these
Regards the grade I don't actually know how to evaluate their difficulty. I've assumed because the puzzle is small and finite the grade range isn't huge. I do know how to test for there being one solution as that's an important puzzle criteria. But get back to me if you have grading ideas.
Edit 24-Feb: Progress saving done; CSS done to show "Page Index" on mobile

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
Page:2025 1 2 :2024 2023 2022 2021 2020 2019 2018 2017
2015 2014 2013 2012 2011 2010 2009 2008 2007 2006
Thank-you everyone for all your questions and contributions.