From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Former featured articleSudoku is a former featured article. Please see the links under Article milestones below for its original nomination page (for older articles, check the nomination archive) and why it was removed.
Main Page trophyThis article appeared on Wikipedia's Main Page as Today's featured article on June 10, 2005.
Article milestones
June 1, 2005Featured article candidatePromoted
October 5, 2006Featured article reviewDemoted
Current status: Former featured article
Wikipedia Version 1.0 Editorial Team  
WikiProject iconThis article has been reviewed by the Version 1.0 Editorial Team.
 ???  This article has not yet received a rating on the quality scale.
 ???  This article has not yet received a rating on the importance scale.
Note icon
This article is Uncategorized.

Third opinion needed[edit]

Someone keeps adding information about a nonnotable Sudoku variant that was apparently created by the person who adds the text mentioning it. (See the original addition by someone called Zanet#### crediting the variant to one "Michel Zanett"). Every time I remove it they just come back and add it back. It'd be helpful if someone else verified that it doesn't belong here. DreamGuy (talk) 19:19, 31 May 2009 (UTC)

Third opinion[edit]

I have been unable to find any reliable source coverage of this variant. One source should be enough for inclusion in the article since it doesn't have to meet the GNG to be part of another article, but instead only has to be verifiable. Without any RS coverage it doesn't belong.

The best way to handle this is to revert and kindly inform the offending party about our policies. If it continues to be added, report the adder for edit warring. --ThaddeusB (talk) 19:44, 31 May 2009 (UTC)

One source would clearly not be enough for a mention here. That's a simply impractical suggestion, as every article would be full of nonnotable nonsense just because it can be confirmed but not because it has any relevance. We're not a collection of trivia. It doesn't have to demonstrate notability for a separate article, but it would still have to be demonstrably notable. One newspaper running a puzzle type or whatever would not cut it. DreamGuy (talk) 16:34, 22 June 2009 (UTC)


Why can't *soduko be a Japanese word? -- (talk) 13:06, 22 June 2009 (UTC)

Because *du becomes zu. —Tamfang (talk) 02:09, 18 September 2009 (UTC)

Suggestions to further improve, 10:28, 17 July 2009 (UTC)[edit]

I read this a bit out of curiosity and saw that it was A-class per WikiProject Mathematics; I'm not convinced. I recommend all of those suggestions, in order, before nominating for good or featured status:

  1. Lead: Simply citing (a translation of) Euler's paper does not prove that Euler is "sometimes incorrectly cited as the source of the puzzle"; who incorrectly cites it? Find a source that says who does and that they're wrong. At minimum (and I don't recommend this as it is construable as original research) explain that the paper only talks about various aspects of Latin squares without inventing the game or its name, and remove the "sometimes incorrectly cited" phrase—Euler's paper doesn't say who does.
  2. History: Consider describing the main variant's rules in a prior section before discussing the game's history, or at least moving "Variants" to precede it. The article body has barely started, and the first paragraph already says "It was not a Sudoku because it contained double-digit numbers and required arithmetic rather than logic to solve"—that probably cost us a reader or two already. Also more weasel words in para 2; there may be more throughout.
  3. Variants: Any Sudoku variants without their own articles need a citation—e.g. give an issue and page number for at least one magazine appearance of Digital Number Place. Anyone can think up a variant and plop it on the page; mention notable ones only. Check that variants with their own article are also cited, and consider copying their articles' citations to this article.
  4. Competitions: The World Sudoku Championships should probably be grouped together, and followed by the newspaper ones.
  5. Stubby paragraphs and lone sentences remain a long-time issue. Combine them with bigger ones.
  6. Cite all non-obvious statements (as in #1) in the article, if possible, and make sure the cites prove those specific facts.
  7. Make sure that the lead summarizes all the article's major aspects. A good lead won't need citations (except for contentious stuff) because it briefly says what's already written.
  8. Add alt text for images so it can meet FA criterion 3.
  9. Seek a peer review and a copyedit from someone outside of the project(s) to point out errors, redundancies, and unfamiliar terms, especially in the lead (many will just read that, so make it sparkle like a bag of golden Skittles).

It's great that the New York Times liked it some years ago, but there is still vast improvement needed here. This isn't about some cancelled, short-lived, direct-to-video cartoon, but a world-famous game; it should be worth its players' time. --an odd name 10:28, 17 July 2009 (UTC) I've demoted it to B-class for those issues. Try to fix them before a re-assess. --an odd name 18:57, 17 July 2009 (UTC)


"Wordoku" redirects here, but there's no explanation of it... Wouldn't that be a good idea? (If I knew what it was, I'd contribute one.) -- SomeAvailableName 09:32, 12 December 2009 (UTC)

Uniqueness of solution[edit]

My understanding is that a proper Sudoku has a unique solution. Is this in fact the case? The article doesn't make this point clear, although section 3 alludes to it. Tayste (talk - contrib) 01:24, 17 December 2009 (UTC)

Solution grids fall into 3 main categories: 'No-solution', caused by an invalid puzzle (some contradiction present); 'one/unique solution', which only have 1 solution that can't be eliminated by logic; and Multiple Solutions, which occur when one (or more) cells are left with more than one possibility that can't be eliminated. Regardless of which possible value you choose, the final puzzles are all both valid and generatable from the given input grid. If you take a grid known to have one or more solutions and erase some of it's inputs, you'll almost always end up with a puzzle with multiple solutions. Thus, a puzzle with multiple solutions could be considered the result of insufficient input data, but is still technically valid. Ghostwo 07:54, 6 June 2010 (UTC)

Missing explanation of difficulty levels.[edit]

In my local newspaper, the standard sudoku (9x9 grid with 3x3 sub-grid) always comes with a given difficulty rating, which ranges from one to five stars – five being the hardest.

It would be nice to have a separate section, in the Sudoku article, with info about difficulty levels in sudoku. But, at the same time, I am a little bit afraid that it might kind of "spoil the fun" – if I explicitly were to know the details of the exact features/qualities which makes up each difficulty level. Therefore I think I might prefer to have some of the most revealing info in a "{{Collapse top}} ''Explicit details'' {{Collapse bottom}}" subsection, with a spoiler warning in front of it.
--Seren-dipper (talk) 02:42, 28 February 2010 (UTC)

There is no such standard by any means. Difficulty level ratings vary wildly among publishers.—Emil J. 11:41, 1 March 2010 (UTC)
Still, presumably, the difficulty level ratings from each publisher is internally consistent – is it not? So it would be interesting to read examples of how some (various) publishers rate their sudokus! -- (talk) 02:09, 6 March 2010 (UTC)

Correlation to Intelligence quotient (IQ) ?[edit]

My subjective experience is that the difficulty, of each of the five difficulty levels mentioned in the previous section, is fairly constant. So, on the condition that a person never just guesses on a number, then the ability to solve each difficulty level, may have at least some probability -correlation with the Intelligence quotient (IQ) of that person. For instance: what would be an educated guess about the IQ-level of one who never manages to solve a four-star? Or one who, given time, always is able to solve a three-star game, but only sometimes manages to solve a four-star. (And what about the other difficulty levels?). (I guess it will make a significant change to his/her ability, whether someone has told the person anything more than the basic rules about how to solve a sudoku, but still I would love to read a little something about this, when reading about sudoku!).
I do not know of any scientific research around this, but I presume it has been done. It would be very nice to have some info about it in this article.
--Seren-dipper (talk) 02:42, 28 February 2010 (UTC)

WHY do you think there ought to be a correlation between sudoku-solving ability and IQ? especially when you have instances of people with autism who have very specific mathematical talents? (talk) 00:37, 12 September 2012 (UTC)
What about the IQ of someone who puts such nonsense on this page? I won't catalog all the logic errors and muddled thinking here, beyond the primary one--it doesn't belong on this page. P.S. The response below is also completely irrelevant to this page ... Wikipedia is based on reliable sources, not the idle musings of editors, and it's bizarre to ask me for sources for an absurd speculation (made 11 years ago) that I'm objecting to. (And don't change the indentation of comments ... I indented this based on who I was responding to. BTW, the comment above by is not off the mark at all. IQ variance being greater in autistics than neurotypicals actually reinforces the point--people with ASD are 40 times as likely to have intellectual disabilities.'s point was (obviously) that even people with severe intellectual disabilities might have specialized abilities for solving Sudoku.) -- (talk) 04:15, 31 March 2021 (UTC)
Easy now ... but yes, IQ is a slippery subject, being an attempt to express in one number what unquestionably is a much more complicated matter. Serious IQ's are typically determined by a battery of different tests, thus attempting to average out the different emphasis of different types of questions. Classical IQ tests (apart from often mixing in things that clearly have a cultural bias that shouldn't be part of a determination of "general intelligence") tend to emphasize things like logical thinking and pattern-finding, and Sudoku-solving would fit nicely into such tests - clearly, it would "measure" some of the same things. For virtually ANY type of question in an IQ test, there are techniques and approaches that can be trained, meaning the test does not only measure "general intelligence", but also measures specific training towards the specific question types in the test. This would be more true about Sudoku solving than for many other question types, so the simple association of Sudoku difficuly levels with IQ is impossible. Completely unfounded and off the top of my head: A person with an IQ of 100, say, can solve a two-star Sudoku without training, but with some training, the same person can solve a four-star Sudoku, and after learning an algorithm involving some kind of note-taking in the process, can solve any solvable Sudoku.
Does this discussion belong on this talk page? That depends: Does it point towards some change or addition to the article itself? The answer to that is: Only if someone can dig up sources of a type and quality suitable for Wikipedia. Can you?
PS. The mention of autism above is way off the mark. Unless I misunderstand, it seems to imply that autists have low IQ, which is nonsense. As measured with classical IQ tests, I'd expect autists to be spread out over all of the IQ scale (possibly even more spread out that neurotypicals).-- (talk) 10:45, 31 March 2021 (UTC)
Article talk pages are primarily about changes to article, but they are also about community interaction. Hence, don't just be right - be civil too, and explain yourself in a way that may help other editors along.-- (talk) 18:42, 2 April 2021 (UTC)

Solving methods?[edit]

Glossary of Sudoku links to Sudoku#Solution methods to explain "scanning", "cross hatching" and "counting", yet the section doesn't seem to exist and none of these terms are explained. What happened? Jpatokal (talk) 07:08, 20 March 2010 (UTC)

The sections on the various strategies used (and on related terminology) were removed during this edit in November 2008. The reason given was that Wikipedia is not an instruction manual and that solutions are already covered in the Mathematics of Sudoku article. Riick (talk) 01:19, 20 April 2010 (UTC)
(Also potentially relevant is this uncaught section blanking vandalism. It may have inspired the removal of the solution methodology sections by eliminating their intended context within the article. Riick (talk) 06:13, 21 April 2010 (UTC) )

The article at the time of the deletions was certainly starting to resemble an instruction manual. However, I do not believe this necessitated deleting all solution methodology. Instead the tone and placement of that content should have been revised so as not to sound like instructions. How people go about using a puzzle is very much part of what the puzzle is, and therefore should be included in the article. In fact, according to the footnote for the Wikipedia is not an instruction manual policy, "describing to the reader how other people or things use something is encyclopedic; instructing the reader in the imperative mood about how to use something is not." I am also not convinced by the second reason given for the deletion. The Mathematics of Sudoku article seems to be about combinatoric studies of Sudoku puzzles. As such, it discusses topics such as calculating the number of different Sudoku puzzles which can be constructed, determining whether it is theoretically possible for a Sudoku puzzle to have a given pattern, and so on. It includes nothing about the various approaches used when solving a Sudoku puzzle, nor did it at the time of the deletion. For these reasons, I propose returning the information about solution methodologies to the article. Riick (talk) 04:31, 21 April 2010 (UTC)

This is not the first time there has been discussion about whether or not solution methodologies should be included. In an archived discussion from 2005 Zotmeister made the following comment, and I think it's still relevant today: "We list the primary weapons people use to tackle Sudoku puzzles because we're supposed to report that - it's historical info. The line is drawn between telling how people solve the puzzle and telling people how to solve the puzzle; we do the former to the best of our ability and leave the latter to other resources." Also, for what it's worth, I found an archived comment from 2008 regarding the specific deletions in question. Riick (talk) 05:26, 21 April 2010 (UTC)

Could someone add back the worthwhile part of the discussion about Sudoko strategies/solutions? The person who deleted them, for example? Deleting all of that, some time ago, bordered on vandalism. The 'instruction manual' rationale does not really apply when specific patterns and strategies have been 'studied' and labelled. In this sense they are comparable to standard encyclopedic discussions of chess (various openings and gambits and so on that have been generally identified and are worthy of discussion). I might draw the line as specific notation systems used by individual solvers. (talk) 09:42, 8 May 2011 (UTC)

I wrote (almost) everything I know about Sudoku Solving on a webpage and a friend translated it into english. The result is exactly intended to be an 'instruction manual'. If someone likes to have more instructions and strategies here a link to my site is an option. A special 'manual' article might be an other option. If parts of my text or pictures are used, please name and/or link the source! — Preceding unsigned comment added by (talk) 15:32, 13 July 2014 (UTC)

Steganography in sudoku[edit]

Let's get rid of this section. Steganography can be performed on pretty much any type of data. There's no evidence that anyone is engaging in steganography in sudoku puzzles other than for the purpose of demonstrating that it could be done. Who's with me? - Richard Cavell (talk) 09:25, 22 August 2010 (UTC)

Broken link[edit]

Reference/link 38 in "Notes", "3rd-place winner disqualified in sudoku scandal", is broken. --Mortense (talk) 18:37, 4 October 2010 (UTC)

Mathematical modeling of sudoku puzzle and easy way to find solution[edit]

I have found a wonderful new method to model the sudoku, it modelled sudoku into any arrey of number ( cordinates ) where by using simple rules we could find solution to any sudoke having valid solution, I think this method is not only good from solving sudoku but would added some many new concepts , solution methoid, mathemacticall way to understand sudoku etc...and need some one to review and help me to post it under right catagory , link is : HarshGoel (talk) 03:49, 17 October 2010 (UTC) Harsh Goel

This is not what this page is for. -- (talk) 06:15, 31 March 2021 (UTC)

Number of classic 9×9 Sudoku solution grids[edit]

The Number of classic 9×9 Sudoku solution grids is 1,908,360,529,573,850,000,000,000,000 or approximately ~ 1.908x1027 (help to verify my finding posted at ( appendix-B page 28 ) HarshGoel (talk)Harsh Goel —Preceding undated comment added 16:54, 27 October 2010 (UTC).

WP:Japan Importance Re-evaluated[edit]

The Importance of Sudoku to WP:Japan has been re-evaluated after secondary opinions were solicited from members of WP:Japan. The article was downgraded for the following reasons:

  • The game of sudoku was NOT invented in Japan.
  • However, the name "Sudoku" was invented in Japan.
  • While the game is an international phenomenon, it should not be considered a "core topic" (per Top-importance criteria) on the subject of Japan. That is, if one were going to go look up information on Sudoku, one would not start with an encyclopedia on Japan.
  • Without sudoku, Japanese history and culture would not be much different, and therefore does not rank among articles such as Toyotomi Hideyoshi, Kabuki, or the Atomic bombings of Hiroshima and Nagasaki (all Top-importance).

Thank you. Boneyard90 (talk) 22:14, 16 May 2011 (UTC)

Grubblegrook added a book promotion in the first section[edit]

I removed it.. but here it is for posterity: In 2009 Len Loullis produced a version called Koudus, the first straight-forward substitution of the letters A to I for numbers. Although this may seem to be pointless, Koudus puzzles are noticeably harder than Sudoku. For some reason to do with cognition letters do not spring to the mind’s eye as rapidly as numbers as it is more accustomed to seeing letters in groups forming words. Melrose Books of Ely ISBN 978 190656161 1

In other edits, he also had a url which I won't repeat, just in case. --JeffryJohnston (talk) 18:02, 9 October 2011 (UTC)


I call those 3×3 squares in a Sudoku grid "sectors". -- Denelson83 05:13, 1 November 2011 (UTC)

What some random person calls something is not relevant to Wikipedia. -- (talk) 06:17, 31 March 2021 (UTC)

Killer Sudoku section[edit]

There is currently a very long Killer Sudoku section that appears to be copied straight from the Killer Sudoku page. I'm not sure, but I think that it is supposed to be replaced with just a link and a short description. I feel uncomfortable doing this myself; would someone with more experience check it out? Shades97 (talk) 23:16, 13 November 2011 (UTC)

I have removed the duplicated content and pointed to the main article with a {{main}} template. The article needs more work. - DVdm (talk) 18:27, 18 December 2011 (UTC)

Talk:Sudoku/links to consider[edit]

This subpage has been nominated for deletion, see Wikipedia:Miscellany for deletion/Talk:Sudoku/links to consider. MER-C 08:29, 23 December 2011 (UTC)


I just simply added two redirects for common mispellings — Preceding unsigned comment added by Shrillpicc100 (talkcontribs) 12:50, 15 May 2012 (UTC)

I removed one. - DVdm (talk) 13:16, 15 May 2012 (UTC)
I was about to remove the other one as well, but someone was there before me. - DVdm (talk) 13:21, 15 May 2012 (UTC)

What are cross-sum sudokus?[edit]

At its current state, the section in the article does not give enough information to understand what these actually are. (talk) 09:38, 26 November 2012 (UTC)

This is roughly 1.2×10−6 times the number of 9×9 Latin squares.[edit]


The Latin square neglect the sub-boxes. To fill a sub-box, where are 9*9*9*9*9*9*9*9*9 = 387.420.489 combinations without any restrictions as in a Latin square. If each digit must occur only once, there are only 9! = 9*8*7*6*5*4*3*2*1 = 362.880 or about thousand times less combinations. Since there are nine sub-boxes, the reduction must be much larger than one thousand times thousand or one million. Franz Scheerer (Olbers) (talk) 17:50, 4 November 2013 (UTC)

Nope, you forgot a Latin Square must have distinct digits along a row/column. Also feel free to check it on your own. To compare, I count 576 Latin squares, in which 288 of them are Sudoku grids; that's exactly half. (You can verify this yourself; only 576, so it will take at most about five hours by hand...) By your thinking we have 4*4*4*4 = 256 combinations in a 2x2 box, while in a Sudoku grid we have 4! = 24 combinations, giving 1/10 from each box and thus there are 1/10000 Sudoku grids among 4x4 Latin squares... — chaotic_iak (talk) 12:10, 10 January 2014 (UTC)
This isn't a blog or forum about the article subject. Please omit personal opinions, calculations, or anything else personal from this page. Wikipedia is based on material from reliable sources, period. -- (talk) 06:25, 31 March 2021 (UTC)

Numberphile external link[edit]

Suggest the following external link be added: Grime, James. "17 and Sudoku Clues". Numberphile. Brady Haran.. Grime is a mathematics professor at the University of Nottingham. The video is a spinoff from The Periodic Table of Videos series created at Nottingham. – S. Rich (talk) 04:53, 2 April 2013 (UTC)

Sections out of order?[edit]

I think the sections are kind of out of order. It's currently History, followed by Variants and Mathematics, and then back to the society with Recent Popularity. I feel like History should be followed by Recent Popularity. Opinions? — chaotic_iak (talk) 12:15, 10 January 2014 (UTC)

Variant ABCDoku?[edit]

What about this variant? ABCDoku. See TuckerResearch (talk) 23:47, 14 January 2015 (UTC)

It seems too different to be called a variant. Jimp 18:05, 18 July 2015 (UTC)
It's a variant but isn't notable. -- (talk) 06:27, 31 March 2021 (UTC)

Uniqueness of grid shown in top right[edit]

I thought a true Sudoku should have a unique solution. If that's the case then the one shown in the top right does not satisfy this - values 2 and 4 could be interchanged at (3,8) & (3,9), (8,3) & (9,3), (8,8) & (9,9). — Preceding unsigned comment added by (talk) 11:38, 1 March 2015 (UTC)

An even simpler counterexample to uniqueness would be to interchange 2 and 4 in positions (5,4), (6,4), (5,7) and (6,7). You are correct, Sudoku solutions are to be unique, so this example is not a valid Sudoku example. The 2 x 2 subsquare that I've pointed out is called an intercalate and unless the four positions of one are in different subsquares, their existence will destroy uniqueness. Bill Cherowitzo (talk) 21:29, 1 March 2015 (UTC)


The intro gives the transliteration of "数独" as "sūdoku" which would be pronounced /suːdoku/. The recording, Listen, however, is clearly neither /suːdoku/ nor the Anglicised /suːdoʊkuː/ the article makes it appear to be but /saːdoku/. Jimp 18:32, 18 July 2015 (UTC)

Link to actual Sudoku puzzles[edit]

It seems reasonable to include the Web Sudoku link (, a Sudoku puzzle generator. — Preceding unsigned comment added by Mpiedrav (talkcontribs) 17:05, 8 August 2015 (UTC)

I submit a link for a Sudoku implemented in a spreadsheet file. Basically the game that runs in either Excel or Open Office. The original concept was to teach kids the power of a spreadsheet while also learning Sudoku (Games implemented on spreadsheets) — Preceding unsigned comment added by Grpistoia (talkcontribs) 03:19, 24 January 2021 (UTC)

Round / circular / circle sudoku[edit]

This variant of sudoku is not mentionned yet Hexagone59 (talk) 20:58, 9 November 2015 (UTC)

panmagic Sudoku[edit]

Hi! You may find some work about panmagic Sudokus at testwiki:user talk:Gangleri/tests/4x4 type square/panmagic Sudoku a part of a multiscript collaboration work; see testwiki:category:4x4 type square. Regards Gangleri (talk) 16:10, 28 November 2015 (UTC)

Standardized Format for Sudoku Images[edit]

Between Sudoku, Mathematics of Sudoku, and Sudoku solving algorithms there are several formats for displaying a Sudoku (even within a single article). If any editors Add new Sudoku images, please go to ***Talk:Mathematics of Sudoku*** to see the suggested format. If comments please do not reply here. All comments on standardizing the format should be in the same Talk place.LithiumFlash (talk) 02:42, 1 April 2017 (UTC)


In a varian tof sudoko have seen, there is added the name Gusuo, and some field ar makred grey, but what does it mean? — Preceding unsigned comment added by (talk) 20:35, 15 October 2018 (UTC)

Sandwich sudoku[edit]

I added this section under "Variants", but it was removed with a comment describing it as a "not notable variant".

Sandwich sudoku specifies for each row and column the total of the numbers in squares between the numbers 1 and 9.[1]


  1. ^ Bellos, Mark (6 May 2019). "Can you solve it? Sandwich sudoku - a new puzzle goes viral". The Guardian. Retrieved 20 July 2019.

Following WP:BRD I come here to discuss.

On consideration, I would now add:

Sandwich sudoku or Between 1 and 9 sudoku specifies for each row and column the total of the numbers in squares between the numbers 1 and 9.[1][2]


  1. ^ Bellos, Mark (6 May 2019). "Can you solve it? Sandwich sudoku - a new puzzle goes viral". The Guardian. Retrieved 20 July 2019.
  2. ^ "Between 1 and 9 Sudoku". Retrieved 21 July 2019.

Any views? PamD 18:34, 21 July 2019 (UTC)

Take a look at this Compilation of Sudoku Variants as well as the following discussion and reference to other list. Should all these variants be included in the main Sudoku page? Is the Sandwich variant more notable than them? (I can't find Sandwich in both lists.) My point is not to pollute the page with variants of questionable popularity. In any case, I will not revert your additions for the second time and will let others decide. Dobrichev (talk) 13:50, 22 July 2019 (UTC)
Do you mean to say "I would not revert your additions if you added them again?" You seem to imply that I added the contested variation twice: I did not. I did revert your reversion of my change to the section heading, as the section already includes 9x9 variants like Jigsaw Sudoku (which I know as Jigsawdoku, though I didn't revert your removal of that, either), which were not covered by the previous section heading. PamD 15:55, 22 July 2019 (UTC)
I see no problem in the section heading. "Variations of grid sizes or region shapes" looks OK. If you add back Sandwich I will not be aggressive and literally will not revert in hope that other editors will. If nobody reverts, then the article will stay polluted like many other articles are (ref. Sudoku solving algorithms, Combinatorial explosion). BTW for the same reason I don't like "Mini Sudoku", "Alphabetical Sudoku", "Hyper Sudoku", and "Twin Sudoku". I didn't revert them because I read them months after they were introduced and saw that nobody else reverted their addition.Dobrichev (talk) 16:32, 22 July 2019 (UTC)