 Place a number from 1 to 9 in each empty cell. (One number per cell.)
 Each row, column and 3x3 box (surrounded by bold outline) should contain each number from 1 to 9.
Sudoku puzzles sometimes come in grids sized 6x6 (using the numbers from 1 to 6); 8x8 (using the numbers from 1 to 8); 10x10 (using the numbers from 1 to 10, or sometimes 0 to 9); 12x12 (using the numbers from 1 to 12, or sometimes 1 to 9 together with A,B,C); 16x16 (using the numbers from 1 to 16, or sometimes 1 to 9 together with the letters from A to G) and 25x25 (using either the numbers from 1 to 25, or the letters from A to Y).
These puzzles use the following sized boxes (surrounded by bold outline) as the third constraint respectively: 3x2, 4x2, 5x2, 4x3, 4x4, 5x5. In all cases, each row, column and box should contain each of the number/letter sets.
(Classic) Sudoku
(Classic) Sudoku
Let's get the ball rolling here. Based heavily on the nikoli wording:
Last edited by detuned on Tue 30 Nov, 2010 3:15 am, edited 6 times in total.

 Posts: 600
 Joined: Tue 29 Jun, 2010 11:41 am
Re: (Classic) Sudoku
Reasonable first cut, but it certainly needs to be specified that 3x3 box means boxes surrounded by a bold outline. A good rule of thumb in instruction writing is to assume your reader has never, ever seen one of these puzzles before.
For my money, variants which differ only in grid size ought to be covered in this thread rather than individual ones, with almost identical sets of standard instructions tailored to each  I believe 6x6, 9x9, 12x12 and 16x16 are all currently being published by at least one national newspaper, I suspect that 8x8 is as well, and 25x25 isn't unheard of (although in my view, it really SHOULD be! ).
For my money, variants which differ only in grid size ought to be covered in this thread rather than individual ones, with almost identical sets of standard instructions tailored to each  I believe 6x6, 9x9, 12x12 and 16x16 are all currently being published by at least one national newspaper, I suspect that 8x8 is as well, and 25x25 isn't unheard of (although in my view, it really SHOULD be! ).

 Posts: 1165
 Joined: Thu 24 Jun, 2010 9:27 pm
 Contact:
Re: (Classic) Sudoku
You can define the puzzle more generally by saying just "boldlined regions" (or some such) instead of specifying the box shapes by dimension. That way you can include all sizes as well as all jigsaw puzzles. Also it allows better for nonsquare boxes, such as 2x3 versus 3x2 in 6x6 Sudoku.nickdeller wrote:For my money, variants which differ only in grid size ought to be covered in this thread rather than individual ones, with almost identical sets of standard instructions tailored to each
Generally I would certainly avoid basing anything on the Nikoli instructions. They are often just plain wrong in English, and there is at least one (I forget which) which omits a critical part of the instructions too. However their worked examples are sometimes fun  I'd use them as a supplementary resource, not a primary source for instructions. (at least in English!)

 Site Admin
 Posts: 2691
 Joined: Fri 18 Jun, 2010 10:45 pm
 Location: Edinburgh, Scotland
Re: (Classic) Sudoku
From WSC 2010 Classics round:
"Place the digits 1 through 9 into the empty cells in the grid (a single digit per
cell) so that each digit appears exactly once in each of the following
regions: the nine rows, the nine columns, and the nine outlined 3×3 regions."
WSC 2009/2008/2006:
"Fill in the grid so that every row, column and 3x3 box contains all the digits from 1 to 9"
WSC 2007:
"Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each
of the rows, columns and the nine outlined 3x3 regions."
I thought this would be simple
"Place the digits 1 through 9 into the empty cells in the grid (a single digit per
cell) so that each digit appears exactly once in each of the following
regions: the nine rows, the nine columns, and the nine outlined 3×3 regions."
WSC 2009/2008/2006:
"Fill in the grid so that every row, column and 3x3 box contains all the digits from 1 to 9"
WSC 2007:
"Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each
of the rows, columns and the nine outlined 3x3 regions."
I thought this would be simple
Re: (Classic) Sudoku
When I'm writing formal instructions, I always imagine that aliens are reading them
For that reason, I would ask them to place one digit into each empty cell
so that each row, each column and each boldoutlined region contains each number from 1 to N "exactly" once.
although even that might be a little ambiguous!!
For that reason, I would ask them to place one digit into each empty cell
so that each row, each column and each boldoutlined region contains each number from 1 to N "exactly" once.
although even that might be a little ambiguous!!
Re: (Classic) Sudoku
It strikes me that the original poster has a lot of power over the rules!
Anyhow, I've updated to allow for different sized puzzles (seems sort of clunky to me, but it does the job). I've stuck with "a digit from 1 to 9" rather than "one digit from 1 to 9" as the former version is clearly nonplural  the latter mixes up numbers in different contexts.
Adding the caveat that each digit should appear exactly once in each of the constraints is superfluous information  which in my mathematical training has always been considered bad style.
Anyhow, I've updated to allow for different sized puzzles (seems sort of clunky to me, but it does the job). I've stuck with "a digit from 1 to 9" rather than "one digit from 1 to 9" as the former version is clearly nonplural  the latter mixes up numbers in different contexts.
Adding the caveat that each digit should appear exactly once in each of the constraints is superfluous information  which in my mathematical training has always been considered bad style.

 Posts: 600
 Joined: Tue 29 Jun, 2010 11:41 am
Re: (Classic) Sudoku
Might be as well to use "number" rather than "digit", neatly solving the problem that 10, 12, 16, 25 et al aren't digits!
Re: (Classic) Sudoku
In the rules as they stand (at the top of the page), there's nothing to prevent me from placing several numbers into one cell (in that I'm not disallowed from doing so)
In fact I could fill up every cell with all of the numbers 19 and I've completed the puzzle according to these rules!
At least one use of the word "exactly" ought to be there.
(plus, this illustrates the general need for an easytounderstand visual example alongside any instructions we give  this, I'd think, is how almost everyone first learned how sudoku really worked)
Having said all of that, Sudoku is a special case. My favourite instruction set would be:
"Sudoku... you know what to do!"
In fact I could fill up every cell with all of the numbers 19 and I've completed the puzzle according to these rules!
At least one use of the word "exactly" ought to be there.
(plus, this illustrates the general need for an easytounderstand visual example alongside any instructions we give  this, I'd think, is how almost everyone first learned how sudoku really worked)
In contrast to mathematics: In my educational training, giving the theoretical minimal set of instructions for people to follow is considered very bad style! The style guide for mathematics understandably asks us to omit unnecessary information, but in puzzling it's highly desirable to make the detail as clear as possible. (or suffer a lengthy Q&A session)Adding the caveat that each digit should appear exactly once in each of the constraints is superfluous information  which in my mathematical training has always been considered bad style.
Having said all of that, Sudoku is a special case. My favourite instruction set would be:
"Sudoku... you know what to do!"
Re: (Classic) Sudoku
I'd avoid grouping Jigsaw/Irregular Sudoku in here, as if there's going to be tips as well, there are extra logical steps with Jigsaw that don't apply to normal  e.g. if in a 9x9 there is a long Lshape (8 cells with a sticky out one) then the sticky out number is the same as the unused cell in the row or column. Apologies for the technical language, but you know what I mean. Hopefully.GarethMoore wrote: You can define the puzzle more generally by saying just "boldlined regions" (or some such) instead of specifying the box shapes by dimension. That way you can include all sizes as well as all jigsaw puzzles. Also it allows better for nonsquare boxes, such as 2x3 versus 3x2 in 6x6 Sudoku.
Re: (Classic) Sudoku
Agree totally regarding tips.drsteve wrote: I'd avoid grouping Jigsaw/Irregular Sudoku in here, as if there's going to be tips as well, there are extra logical steps with Jigsaw that don't apply to normal  e.g. if in a 9x9 there is a long Lshape (8 cells with a sticky out one) then the sticky out number is the same as the unused cell in the row or column. Apologies for the technical language, but you know what I mean. Hopefully.
However, if we are writing a set of rules for publication, then I prefer Gareth's wording
(even though that also applies to a more general puzzle type)