Feedback and Questions

Why doesn't your solver utilize multi chain coloring techniques? I see singles chaining and bivalue cell color chaining (3D Medusa). I'm new to Sudokus, and wondering if multicoloring is a poor technique, or if there are better techniques that take place of multicoloring? Thanks, you step by step sudoku solver with explanations, this has made learning the advanced techniques easy.

I have enjoyed the Solver for several years:
(1) to check my answers for puzzles-without-solutions;
(2) help me improve my solving ability;
(3) nudge me forward when I get stuck with a particular puzzle; and
(4) check Solution Count.

Today I solved a puzzle, checked my solution and found my solution missing in Solver's Solution Count. This suggests an obvious question: Solution Count isn't necessarily exhaustive, correct?

Dear Stuart,
I have been using your ios app for quite sometime now. Due to IOS 12 upgrade, I am not able to use it. Can you upload a new version with 64 bit support for people who have purchased it earlier.

Regards
Karthik Raj

There is a Killer Sudoku board I would like you to look at

Click on this link:
LINK

I am at my wit's (such as it is) end having spent far too much time on this one.
It comes from Stefan Heine Killer Sudoku Hardcore #4.
If you can suggest an approach or another site where I might be able to solicit assistance, I would very much appreciate it. Thank you.
Michel

once it put the pencilmarks in it worked..Good to see it up and running!

Andrew,

I have a problem with your excellent Sudoku Solver. It occurs on all Sudoku's I try to solve.

Above the left small board I select "enter clues". Under the left small board, I have "auto tab" and "auto clear" checked.

Next, in the big board, I edit candidates in some square. E.g. I edit C3 from "1234" to "12". When I then go to the small board, and enter a value in some square, candidates in C3 automaticallly jump back from "12" to "1234".

I do not understand this. Am I doing something wrong? Is this an error in your program?

This does not seem to happen when I uncheck the "auto clear" field.

My understanding of the "auto clear" checkbox is that all impossiblle candidates are automaticallly removed after entering a solution or after a square is solved.

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Furthermore, I do not understand what you mean by "Enter clues () or solutions ()". What is the difference?

Kind regards,

Gert de Korte, Utrecht, Netherlands.

Hi Andrew. Are there theoretical limits to how few numbers can be present initially to produce a unique solution? Are there algorithms for producing solvable sudokus, or is a trial and error approach necessary? More generally, has the game been thoroughly analyzed mathematically?

Thanks for your great site and for maintaining it over the years!

I have been solving Sudoku Puzzles for about six months and enjoying them very much. I came across this puzzle where you can use the wxyz technique. The explanations you provide to use this technique shows four examples. In the puzzle I sent you, examples 1 & 2 from your documentation, are combined creating 2 digits as the "non-restricted common digit." This allows the elimination of 2 digits as apposed to only one digit shown in your explanations. I don't know if this is common but it deviated from your explanations and I thought you might be interested in this modification. In addition, this wxyz technique is not needed to solve this puzzle.

Thank you for you online tutelage over these last 12 years. In 2005 I was diagnosed and treated for a year to clear up some nasty cancer.

I took that year to learn Sudoku because logic is not a strength of mine...it helped sort many things out for me.

I took off a few years from the puzzles as I returned to work and prepared for a fun redirection after 37 teaching elementary students.

Now I come back and am grateful that when I get stuck on a puzzle your site will be there to help me...on so many levels & Sudoku puzzle styles.

Hello, many thanks for your sudoku site, solver and methodology which are so well done and instructive.
I have learnt a lot with them.
I have faced a problem since some weeks as the board which retrieves solutions was changed so that the grid 9/9 has become 5/10. Therefore, it is impossible to read the solutions proposed by the solver so far.
Thank you very much for your help.
Serge