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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 @ 2017-05-16 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: 131
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: 324
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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