Surplus / Deficit Sudoku [WSC 2018, lots of other contests]

Post Reply

Is this suitable for a Sudoku competition?

Yes - no restrictions, including mixed surplus/deficit regions
3
23%
Both, but only as purely deficit or purely surplus, with no further restrictions
3
23%
Both, with the added restriction deficit regions have size N-1 and surplus regions have size N+1
4
31%
Surplus Only
0
No votes
Deficit Only
0
No votes
Maybe
1
8%
No
2
15%
 
Total votes: 13

Realshaggy
Posts: 20
Joined: Sun 29 Apr, 2012 2:21 pm

Surplus / Deficit Sudoku [WSC 2018, lots of other contests]

Post by Realshaggy » Wed 02 Jan, 2019 12:37 pm

These puzzles have been regulary used in contests since their invention. They usually come in pairs and also usually are not bigger than 7x7 with region size n+1 for the Surplus and region size n-1 for the Deficit Sudoku. Because solving becomes rather ugly and error-prone after that and it is possibly to make difficult puzzles even in small sizes. For these reasons, I think they should also be posted together here.

Rules (Surplus Sudoku): Place the digits from 1 tot 7 in every row and column. Every bold outlined region of eight cells contains all digits at least once.

0002FU-1.png
0002FU-1.png (11.55 KiB) Viewed 4273 times

Rules (Deficit Sudoku): Place the digits from 1 tot 7 in every row and column. Digits may not repeat in the bold outlined areas.

3068-1.png
3068-1.png (10.49 KiB) Viewed 4273 times

The examples are taken from Richards weekly sudoku Variant Series at the puzzle portal of Logic Masters Germany.

https://logic-masters.de/Raetselportal/ ... &id=0002FU
https://logic-masters.de/Raetselportal/ ... &id=0002D8

Thomas posted a lot of background information on his Grandmaster puzzles-blog, but since I'm not 100% sure, if giving the reference is enough to meet copyright restrictions, I chose a different picture as example. Richard will not sue me for sure :D

https://www.gmpuzzles.com/blog/sudoku-r ... -and-info/

In addition to violating the "each digit exactly once per region"-rule in different directions, these puzzles also feature cells that are not part of any region.

Going further, there are a lot of additional variants that change the region size and violate the "exactly once per region"-rule in different directions. As an example see "Countdown Sudoku" from WSC 2010. I'm not sure, where to draw the line, to give them an extra topic.
Last edited by Realshaggy on Wed 02 Jan, 2019 2:30 pm, edited 1 time in total.

detuned
Posts: 1954
Joined: Mon 21 Jun, 2010 2:25 pm
Location: London, UK
Contact:

Re: Surplus / Deficit Sudoku [WSC 2018, lots of other contests]

Post by detuned » Wed 02 Jan, 2019 2:20 pm

Realshaggy wrote:
Wed 02 Jan, 2019 12:37 pm
Thomas posted a lot of background information on his Grandmaster puzzles-blog, but since I'm not 100% sure, if giving the reference is enough to meet copyright restrictions, I chose a different picture as example. Richard will not sue me for sure :D

https://www.gmpuzzles.com/blog/sudoku-r ... -and-info/
I'm sure Thomas will not sue you either. The content on the GM puzzles blog is covered by the following licence: https://creativecommons.org/licenses/by ... deed.en_US


I've also seen some examples where you have both surplus and deficit regions within the same puzzle. The regional constraint gets much weaker the smaller the deficit regions get, and the bigger the surplus regions get, and so the N +/- 1 constraint seems like a sensible constraint to me with a puzzle maker's hat on. However, I have certainly heard opinions that both should not count as sudoku, particularly surplus sudoku as it allows for numbers to be repeated within regions.

detuned
Posts: 1954
Joined: Mon 21 Jun, 2010 2:25 pm
Location: London, UK
Contact:

Re: Surplus / Deficit Sudoku [WSC 2018, lots of other contests]

Post by detuned » Wed 02 Jan, 2019 2:33 pm

Apologies for the multi-dimensional nature of the poll. I hope to have given a good representation to different views on this one, but when we are talking about several examples all at once it becomes hard to specifically tailor the poll to cover all bases. If you happen to feel differently to any of the options listed above, please do leave a comment

Realshaggy
Posts: 20
Joined: Sun 29 Apr, 2012 2:21 pm

Re: Surplus / Deficit Sudoku [WSC 2018, lots of other contests]

Post by Realshaggy » Wed 02 Jan, 2019 2:51 pm

I wasn't sure, if I should post them each on their own. But as far as I can remember, they almost always come as a pair in a contest. What makes sense, because mixed regions would eliminate a lot of the nice extra logic that comes with all n+1/n-1 regions. If you don't use that, there is not much more left than one ugly puzzle. Might be a challenge for authors to use mixed regions and still make an appealing puzzle.
(And the "sueing" was a joke, just to be sure if that was not clear enough. )

Post Reply