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What is a Sudoku
   WSC and WPC 2017 -> General Discussion about WSC and WPC 20177 posts • Page 1 of 1 • 1
Subject: RE: What is a Sudoku @ 2017-01-30 11:55 AM (#22406 - in reply to #22342) (#22406) Top

WSPC Organizer

Posts: 739
Location: India
We agree that the simplicity of the basic rules are the essence of a sudoku and in a World Sudoku Championship all (or almost all) sudokus should follow these basic rules.

However at the same time we should not limit the creativity of sudoku creators who can tweak the rules a bit yet retain the essence of a sudoku.

Specifically answering the edge cases that you described.
· Repetition of digits – All sudokus have non-repeating digits in rows, columns and outlined regions, except one sudoku in a team round where each digit appears twice, and (maybe) one sudoku in an individual round which is a popular variant, like Surplus Sudoku.
· Outlined regions – In all sudokus the outlined regions cover the entire grid and there is no sudoku with a single cell as a region, except (maybe) one or two popular variants like Scattered Sudoku or Deficit Sudoku.

In either case, the number and points of such sudokus is negligible in context of the whole WSC.

I think we differ in opinion on the Skyscrapers puzzle not being a hybrid. As an experienced solver with prolonged exposure to Skyscraper Sudokus the variant has become fairly standard, but at the root it is still a hybrid. As to illustrate our point about the influence of the sudoku creator, here are two examples, the first one is like what we described earlier, a sudoku with skyscraper constraints and the second one, a skyscraper puzzle with sudoku constraints.

1. http://2.bp.blogspot.com/-T1n7_D6l3sw/ULZg5c7I0MI/AAAAAAAAA84/iNQow...
2. http://wspc2017.logicmastersindia.com/images/Skyscraper.P.png

Also to be clear as authors we have decided to not include any hybrid variant which does not naturally fit into a sudoku solving experience. This mean we have avoided hybrids which do not relate to any other sudoku type. Also we have tested the sudokus with test solvers who do not have a puzzle solving background to ensure that there is no bias towards additional puzzle solving skills.

We also agree that the loop example shared by you from the LMI test is not suitable for a WSC.

Also as per our current estimate of all the sudoku types we expect that such hybrid puzzles (including Skyscrapers Sudoku, Kropki Sudoku, etc.) cover about 4% of the total points in the competition.

Overall I am not sure whether these answers would convince you to participate or not, but the answers reflect our thought process as sudoku creators. At LMI we have not been afraid to experiment and in my opinion most experiments have been successful because of the extensive testing / feedback that we collect to ensure that the experiment is well received. We will leave it to your best judgement to trust our experience in ensuring a fair and unbiased competition while allowing for a certain degree of innovation.

P.S: Sorry for the delay in the response, the last couple of weeks have been hectic with our efforts to finalize the puzzle booklets for a majority of the rounds.
Subject: RE: What is a Sudoku @ 2017-01-30 2:54 PM (#22409 - in reply to #22406) (#22409) Top

Diagonal Vision Author

Posts: 337
Location: Switzerland
Thank you very much for your detailed answer.
See you in Bangalore ;)

Subject: Re: What is a Sudoku @ 2017-05-16 3:11 PM (#22933 - in reply to #22334) (#22933) Top

Posts: 1

Location: India
Thank you but really i love this game
Subject: Re: What is a Sudoku @ 2017-06-06 4:13 AM (#22959 - in reply to #22334) (#22959) Top

Posts: 152
Location: United Kingdom
I've only just seen this thread. On the back of a very lively discussion on my blog between now and this original post, I don't want to kick up any more hornets nests.

However, I do want to ask a more philosophical question.

In the rules of classic sudoku, placed numbers must appear exactly once in each row, column and 3x3 box. This is sometimes characterised as "non-repetition", so that we might instead insist that placed numbers appear at most once in each row, column and 3x3 box.

However, this is not as often characterised as "inclusion" - in other words we require placed numbers to appear at least once in each row, column and 3x3 box. And yet, to my eyes, this is an equally good characterisation of the rules. Why is it that "non-repetition" has more prominence as a sudoku solving concept when compared to that of "inclusion"?

I definitely find it curious when people can accept deficit sudoku as bona fide sudoku, and surplus as being somewhat questionable. Perhaps this particular line of thinking sheds some light on the matter.
Subject: Re: What is a Sudoku @ 2017-06-18 5:46 PM (#22968 - in reply to #22959) (#22968) Top

Diagonal Vision Author

Posts: 337
Location: Switzerland
Just a few words (I don't plan to be very active on this subject in the future, as I think I've said almost everything I wanted to say in the past few years).

In my opinion, both characterisations "non-repetition" and "inclusion" are equally important, and both ARE important. I'm surprised to read that some people make a hierarchy between those, I never heard it before.
On a philosophical plan, I don't see any reason to say that a puzzle which hasn't these 2 characteristics is a sudoku.

On the other side, if we want to allow these puzzles into sudoku competition, I think we should be more precise about the definition of deficit and surplus sudoku.

While I'm not annoyed by "standard" deficit/surplus, I mean deficit having N+1 deficit regions containing each N-1 cells and surplus having N-1 surplus regions containing each N+1 cells (Well, I've to say that I personally prefer when these puzzles are smaller than 9*9). I would be unhappy to see the processus pushed to extreme: I already said it's crucial for me that regions cover the whole grid (or almost the whole grid), I would add that a 9*9 deficit sudoku having 27 deficit regions of 3 cells or 9*9 surplus sudoku having 3 big regions of 27 cells would be far from what I expect a sudoku should be (but isn't contradictory with deficit/surplus definition and doesn't break more characteristic of classic sudoku than "standard" deficit/surplus sudoku, apart from size of regions being far from number of symbols to be placed).

Again, I think it's the responsibility of the WPF/organizers/authors to say which kind of puzzles are called sudoku, if it exceeds largely what is commonly accepted by everybody (and I mean everybody, not everybody in the puzzle community, as we are speaking here about a World Championship, not only an annual tournament of puzzle enthousiasts). Still waiting the WPF to say a single word on this subject...

Of course, this is again only my personal opinion.

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