In 1997, retired Hong Kong judge Wayne Gould, 59, a New Zealander, saw a partly completed puzzle in a Japanese bookshop. Over six years he developed a computer program to produce puzzles quickly. Knowing that British newspapers have a long history of publishing crosswords and other puzzles, he promoted Sudoku to The Times in Britain, which launched it on 12 November 2004 (calling it Su Doku). The first letter to The Times regarding Su Doku was published the following day on 13 November from Ian Payn of Brentford, complaining that the puzzle had caused him to miss his stop on the tube.[19]
The rapid rise of Sudoku in Britain from relative obscurity to a front-page feature in national newspapers attracted commentary in the media and parody (such as when The Guardian's G2 section advertised itself as the first newspaper supplement with a Sudoku grid on every page[20] ). Recognizing the different psychological appeals of easy and difficult puzzles, The Times introduced both side by side on 20 June 2005. From July 2005, Channel 4 included a daily Sudoku game in their Teletext service. On 2 August, the BBC's programme guide Radio Times featured a weekly Super Sudoku which features a 16×16 grid.
In the United States, the first newspaper to publish a Sudoku puzzle by Wayne Gould was The Conway Daily Sun (New Hampshire), in 2004.[21]
The world's first live TV Sudoku show, 1 July 2005, Sky One.
The world's first live TV Sudoku show, Sudoku Live, was a puzzle contest first broadcast on 1 July 2005 on Sky One. It was presented by Carol Vorderman. Nine teams of nine players (with one celebrity in each team) representing geographical regions competed to solve a puzzle. Each player had a hand-held device for entering numbers corresponding to answers for four cells. Phil Kollin of Winchelsea, England was the series grand prize winner taking home over £23,000 over a series of games. The audience at home was in a separate interactive competition, which was won by Hannah Withey of Cheshire.
Later in 2005, the BBC launched SUDO-Q, a game
show that combines Sudoku with general knowledge. However, it uses only 4×4 and 6×6 puzzles.
In 2006, a Sudoku website published songwriter Peter Levy's Sudoku tribute song,[22] but quickly had to take down the mp3 due to heavy traffic. British and Australian radio picked up the song, which is to feature in a British-made Sudoku documentary. The Japanese Embassy also nominated the song for an award, with Levy doing talks with Sony in Japan to release the song as a single.[23]
Sudoku software is very popular on PCs, websites, and mobile phones. It comes with many distributions of Linux.
Software has also been released on video game consoles, such as the Nintendo DS, PlayStation Portable, the Game Boy Advance, Xbox Live Arcade, several iPod models, and the iPhone. In fact, just two weeks after Apple, Inc.
debuted the online App Store within its iTunes store on July 11, 2008, there were already nearly 30 different Sudoku games, created by various software developers, specifically for the iPhone and iPod Touch. One of the most popular video games featuring Sudoku is Brain Age: Train Your Brain in Minutes a Day!. Critically and commercially well received, it generated particular praise for its Sudoku implementation[24][25][26] and sold more than 8 million copies worldwide.[27] Due to its popularity, Nintendo made a second Brain Age game titled Brain Age2, which has over 100 new sudoku puzzles and other activities.
In June 2008 an Australian drugs-related jury trial costing over AU$1 000 000 was aborted when it was discovered that five of the twelve jurors had been playing Sudoku instead of listening to evidence.[28]
Sudoku 144
Competitions
• The first World Sudoku Championship was held in Lucca, Italy, from March 10–12, 2006. The winner was Jana Tylová of the Czech Republic.[29] The competition included numerous variants.[30]
• The second World Sudoku Championship was held in Prague from March 28 to April 1, 2007.[31] The individual champion was Thomas Snyder of the USA. The team champion was Japan.[32]
• The third World Sudoku Championship was held in Goa, India, from April 14–16, 2008. Thomas Snyder repeated as the individual overall champion, and also won the first ever Classic Trophy (a subset of the competition counting only classic Sudoku). The Czech Republic won the team competition.[33]
• The fourth World Sudoku Championship was held in Žilina, Slovakia, from April 24–27, 2009. After past champion Thomas Snyder of USA won the general qualification, Jan Mrozowski of Poland emerged from a 36-competitor playoff to become the new World Sudoku Champion. Host nation Slovakia emerged as the top team in a separate competition of three-membered squads.[34]
• The fifth World Sudoku Championship was held in Philadelphia, USA from April 29-May 2, 2010. Jan Mrozowski of Poland successfully defended his world title in the individual competition while Germany won a separate team event. The puzzles were written by Thomas Snyder and Wei-Hwa Huang, both past US Sudoku champions.[35]
• In the United States, The Philadelphia Inquirer Sudoku National Championship has been held three times, each time offering a $10,000 prize to the advanced division winner and a spot on the U.S. National Sudoku Team traveling to the world championships. Puzzlemaster Will Shortz has served as tournament host. The winners of the event have been Thomas Snyder (2007),[36] Wei-Hwa Huang (2008), and Tammy McLeod (2009).[37] In the most recent event, the third place finalist in the advanced division, Eugene Varshavsky, performed quite poorly onstage after setting a very fast qualifying time on paper, which caught the attention of organizers and
competitors including past champion Thomas Snyder who requested organizers reconsider his results due to a suspicion of cheating.[37] Following an investigation and a retest of Varshavsky, the organizers disqualified him and awarded Chris Narrikkattu third place.[37]
See also
• 36 cube
• Algorithmics of Sudoku
• Futoshiki
• Hidato
• Kakuro
• KenKen
• Killer sudoku
• Latin square
• List of Nikoli puzzle types
• List of Sudoku terms and jargon
• Logic puzzle
• Mathematics of Sudoku
• Nonogram (aka Paint by numbers, O'ekaki)
• Sudoku Cube (3D variant)
Sudoku 145
Further reading
• Delahaye, Jean-Paul, "The Science Behind Sudoku" [38], Scientific American magazine, June 2006.
• Kim, Scott, "The Science of Sudoku" [39], 2006
• Provan, J. Scott, "Sudoku: Strategy Versus Structure", American Mathematical Monthly, October 2009. Published also as a University of North Carolina technical report UNC/STOR/08/04 [40], 2008.
External links
• Sudoku [41] at the Open Directory Project – An active listing of Sudoku links.
• Father of Sudoku puzzles next move [42] BBC
References
[1] Arnoldy, Ben. "Sudoku Strategies" (http://www.csmonitor.com/homeforum/sudoku.html). The Home Forum (The Christian Science Monitor). . Retrieved February 18, 2009.
[2] Schaschek, Sarah (March 22, 2006). "Sudoku champ's surprise victory" (http://web.archive.org/web/20060813145953/http://www.
praguepost.com/P03/2006/Art/0323/news5.php). The Prague Post. . Retrieved February 18, 2009.
[3] Lawler, E.L.; Jan Karel Lenstra, A. H. G. Rinnooy Kan, D. B. Shmoys (1985). The Traveling Salesman problem – A Guided Tour of Combinatorial Optimization. John Wiley & Sons. ISBN 0471904139.
[4] Sudoku.name (http://www.sudoku.name/rules/en)
[5] Brian Hayes (2006). Unwed Numbers. 94. American Scientist. pp. 12–15.
[6] So you thought Sudoku came from the Land of the Rising Sun ... (http://www.guardian.co.uk/media/2005/may/15/pressandpublishing.
usnews) The puzzle gripping the nation actually began at a small New York magazine by David Smith The Observer, Sunday May 15, 2005 Accessed June 13, 2008
[7] Boyer, Christian (May 2006). "Supplément de l’article « Les ancêtres français du sudoku »" (http://cboyer.club.fr/multimagie/
SupplAncetresSudoku.pdf) (PDF). Pour la Science: 1–6. . Retrieved 3 August 2009.
[8] Boyer, Christian (2007). "Sudoku's French ancestors" (http://cboyer.club.fr/multimagie//English/SudokuAncestors.htm). . Retrieved 3 August 2009.
[9] Malvern, Jack (2006-06-03). "Les fiendish French beat us to Su Doku" (http://www.timesonline.co.uk/article/0,,2-2208881,00.html).
Times Online (London). . Retrieved 2006-09-16.
[10] Pegg, Ed, Jr. (2005-09-15). "Ed Pegg Jr.'s Math Games: Sudoku Variations" (http://www.maa.org/editorial/mathgames/
mathgames_09_05_05.html). MAA Online. The Mathematical Association of America. . Retrieved October 3, 2006.
[11] "Combinatorial question on 9×9" (http://groups.google.co.uk/group/rec.puzzles/browse_thread/thread/3ba62ed2d76a052/
94ce2b94b84f4e53?lnk=st&q=6670903752021072936960++#94ce2b94b84f4e53). Google newsgroups archive. . Retrieved September 2003.
[12] http://en.wikipedia.org/wiki/Oeis%3Aa107739
[13] Jarvis, Frazer (2006-07-31). "Sudoku enumeration problems" (http://www.afjarvis.staff.shef.ac.uk/sudoku/). Frazer Jarvis's home page. . Retrieved September 16, 2006.
[14] Jarvis, Frazer; Ed Russell (2005-09-07). "There are 5472730538 essentially different Sudoku grids ... and the Sudoku symmetry group"
(http://www.afjarvis.staff.shef.ac.uk/sudoku/sudgroup.html). Frazer Jarvis's home page. . Retrieved September 16, 2006.
[15] http://en.wikipedia.org/wiki/Oeis%3Aa109741
[16] "プログラミングパズルに関心のある人は雑談しましょう" (http://www2.ic-net.or.jp/~takaken/auto/guest/bbs46.html) (in Japanese). プログラミングパズル雑談コーナー / Programming Puzzle Idle Talk Corner. . Retrieved September 16, 2006.
[17] Royle, Gordon. "Minimum Sudoku" (http://www.csse.uwa.edu.au/~gordon/sudokumin.php). . Retrieved September 16, 2006.
[18] Paul K. Newton and Stephen A. DeSalvo. The Shannon entropy of Sudoku matrices Proceedings of the Royal Society A. doi:
10.1098/rspa.2009.0522.
[19] Timesonline.co.uk (http://www.timesonline.co.uk/tol/comment/letters/article390381.ece)
[20] "G2, home of the discerning Sudoku addict" (http://www.guardian.co.uk/g2/story/0,,1482817,00.html). The Guardian (London:
Guardian Newspapers Limited). 2005-05-13. . Retrieved 2006-09-16.
[21] New York Times corrections column, April 2, 2007, p. A2
[22] "Sudoku the song, by Peter Levy" (http://www.sudoku.org.uk/news.htm). Sudoku.org.uk. 2006-08-17. . Retrieved 2008-10-05.
[23] "Hit Song Has the Numbers" (http://www.news.com.au/heraldsun/story/0,21985,20152238-28957,00.html). The Herald Sun.
2006-08-17. . Retrieved 2008-10-05.
[24] Gamerankings.com (http://www.gamerankings.com/htmlpages2/931667.asp)
[25] Gamespot.com (http://www.gamespot.com/ds/puzzle/brainagetrainyourbraininminutesaday/review.html) [26] IGN.com (http://ds.ign.com/articles/702/702057p1.html)
[27] Gamespot.com (http://www.gamespot.com/news/6160557.html)
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[28] Knox, Malcolm (2008-06-11). "The game's up: jurors playing Sudoku abort trial" (http://www.smh.com.au/news/national/
jurors-get-1-million-trial-aborted/2008/06/10/1212863636766.html). The Sydney Morning Herald. . Retrieved 2008-06-11.
[29] "Sudoku title for Czech accountant" (http://news.bbc.co.uk/1/hi/world/europe/4797540.stm) (Free). BBC NEWS. 2006-03-11. . Retrieved 2006-09-11.
[30] "World Sudoku Championship 2006 Instructions Booklet" (http://news.bbc.co.uk/2/shared/bsp/hi/pdfs/10_03_06_sudoku.pdf) (PDF). BBC News. . Retrieved 2010-05-24.
[31] "Report on the 8th General Assembly of the World Puzzle Federation" (http://www.worldpuzzle.org/championships/2006/report.html) (Free). WPF. 2006-10-30. . Retrieved 2006-11-15.
[32] "Thomas Snyder wins World Sudoku Championship" (http://wpc.puzzles.com/press/index.htm#2007-2). US Puzzle Team. 2007-03-31. . Retrieved 2008-04-18.
[33] Harvey, Michael (2008-04-17). "It’s a puzzle but sun, sea and beer can’t compete with Sudoku for British team" (http://entertainment.
timesonline.co.uk/tol/arts_and_entertainment/games_and_puzzles/article3761511.ece). TimesOnline (London). . Retrieved 2008-04-18.
[34] Malvern, Jack (2009-04-27). "Su Doku battle goes a little off the wall" (http://entertainment.timesonline.co.uk/tol/
arts_and_entertainment/games_and_puzzles/sudoku/article6175809.ece). TimesOnline (London). . Retrieved 2009-04-27.
[35] "Pole, 23, repeats as Sudoku world champ" (http://www.philly.com/philly/news/local/92606119.html). PhillyInquirer. 2009-05-02. . Retrieved 2009-05-03.
[36] "Thomas Snyder, World Sudoku champion" (http://www.philly.com/philly/comics_games/sudoku/
Thomas_Snyder__World_Sudoku_champion.html) (Free). Philadelphia Inquirer. 2007-10-21. . Retrieved 2007-10-21.
[37] "Going for 2d, she wins 1st" (http://www.philly.com/philly/news/local/65922787.html) (Free). Philadelphia Inquirer. 2009-10-25. . Retrieved 2009-10-27.
[38] http://www.cs.virginia.edu/~robins/The_Science_Behind_SudoKu.pdf
[39] http://www.scottkim.com/thinkinggames/exploratorium06/the-science-of-sudoku.html [40] http://stat-or.unc.edu/research/Current%20Reports/techpdf/TR_08_04.pdf
[41] http://www.dmoz.org/Games/Puzzles/Brain_Teasers/Sudoku/
[42] http://news.bbc.co.uk/2/hi/asia-pacific/6745433.stm
Mathematics of Sudoku
The class of Sudoku puzzles consists of a partially completed row-column grid of cells partitioned into N regions each of size N cells, to be filled in using a prescribed set of N distinct symbols (typically the numbers {1, ..., N}), so that each row, column and region contains exactly one of each element of the set. The puzzle can be investigated using mathematics.
Overview
The mathematical analysis of Sudoku falls into two main areas: analyzing the properties of a) completed grids and b) puzzles. Grid analysis has largely focused on counting (enumerating) possible solutions for different variants. Puzzle analysis centers on the initial given values. The techniques used in either are largely the same: combinatorics and permutation group theory, augmented by the dexterous application of programming tools.
There are many Sudoku variants, (partially) characterized by the size (N) and shape of their regions. For classic Sudoku, N=9 and the regions are 3x3 squares (blocks). A rectangular Sudoku uses rectangular regions of row-column dimension R×C. For R×1 (and 1×C), i.e. where the region is a row or column, Sudoku becomes a Latin square.
Other Sudoku variants also exist, such as those with irregularly-shaped regions or with additional constraints (hypercube) or different (Samunamupure) constraint types. See Sudoku - Variants for a discussion of variants and Sudoku terms and jargon for an expanded listing.
The mathematics of Sudoku is a relatively new area of exploration, mirroring the popularity of Sudoku itself.
NP-completeness was documented late 2002 [1] , enumeration results began appearing in May 2005 [2] .
In contrast with the two main mathematical approaches of Sudoku mentioned above, an approach resting on mathematical logic and dealing with the resolution of the puzzles from the viewpoint of a player has recently been proposed in Denis Berthier's book "The Hidden Logic of Sudoku". This formalizes certain mathematical symmetries
Mathematics of Sudoku 147
of the game and elicits resolution rules based on them, such as "hidden xy-chains".