A sudoku puzzle...

...and its solution numbers marked in red

Sudoku (数独, sūdoku^?) listen (help·info) is a logic-based placement puzzle. The objective is to fill the 9x9 grid so that each column, each row, and each of the nine 3x3 boxes contains the digits 1 to 9. The puzzle setter provides a partially completed grid so that there is only one solution. Image File history File links Sudoku-by-L2G-20050714. ... Image File history File links Sudoku-by-L2G-20050714. ... Image File history File links Sudoku-by-L2G-20050714_solution. ... Image File history File links Sudoku-by-L2G-20050714_solution. ... Logic, from Classical Greek λόγος logos (the word), is the study of patterns found in reasoning. ... A puzzle is a problem or enigma that challenges ingenuity. ...

Completed Sudoku puzzles are a type of Latin square, with an additional constraint on the contents of individual regions. Leonhard Euler is sometimes cited as the source of the puzzle, based on his work with Latin squares^[1]. A Latin square is an n × n table filled with n different symbols in such a way that each symbol occurs exactly once in each row and exactly once in each column. ... Euler redirects here. ...

The modern puzzle was invented by an American, Howard Garns, in 1979 and published by Dell Magazines under the name "Number Place"^[2]. It became popular in Japan in 1986, when it was published by Nikoli and given the name Sudoku. It became an international hit in 2005. For the Smashing Pumpkins song, see 1979 (song). ... Dell Magazines is a company founded by George T. Delacorte Jr. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... Nikoli (ニコリ) is a Japanese publisher that specializes in games and, especially, logic puzzles. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ...

Introduction

The name "Sudoku" is the Japanese abbreviation of a longer phrase, "suji wa dokushin ni kagiru" (数字は独身に限る, "suji wa dokushin ni kagiru"^?), meaning "the digits must occur only once"^{[3][4][5][6][7][8]}. It is a trademark of puzzle publisher Nikoli Co. Ltd. in Japan.^[9] In Japanese, the word is pronounced [sɯːdokɯ]; in English, it is usually spoken with an Anglicised pronunciation, [səˈdəʊkuː] (BrE) [səˈdoʊkuː] (AmE) or [ˈsuːdəʊku] (BrE) [ˈsuːdoʊku] (AmE) (See IPA (International Phonetic Alphabet) or IPA chart for English for notation usage.) Other Japanese publishers refer to the puzzle as Number Place, the original U.S. title, or as "Nanpure" for short.^[10] Some non-Japanese publishers spell the title as "Su Doku". Nikoli (ニコリ) is a Japanese publisher that specializes in games and, especially, logic puzzles. ... The English language is a West Germanic language that originates in England. ... Diagram showing the geographical locations of selected languages and dialects of the British Isles. ... English language spread in the United States. ... Diagram showing the geographical locations of selected languages and dialects of the British Isles. ... English language spread in the United States. ... For information on how to read IPA transcriptions of English words see here. ... This is a concise version of the International Phonetic Alphabet for English sounds. ...

The numerals in Sudoku puzzles are used for convenience; arithmetic relationships between numerals are irrelevant. Any set of distinct symbols will do; letters, shapes, or colours may be used without altering the rules. In fact, ESPN published Sudoku puzzles substituting the positions on a baseball field for the numbers 1–9. Dell Magazines, the puzzle's originator, has been using numerals for Number Place in its magazines since they first published it in 1979.^[10] ESPN (an acronym for the Entertainment and Sports Programming Network) is an American cable television network dedicated to broadcasting sports-related programming 24 hours a day. ... Dell Magazines is a company founded by George T. Delacorte Jr. ...

The attraction of the puzzle is that the rules are simple, yet the line of reasoning required to solve the puzzle may be complex. The level of difficulty can be selected to suit the audience. The puzzles are often available free from published sources and may be custom-made using software.

Solution methods

The strategy for solving a puzzle may be regarded as comprising a combination of three processes: scanning, marking up, and analyzing.

The top right region must contain a 5. By hatching across and up from 5s elsewhere, the solver can eliminate all the empty cells in the region which cannot contain a 5. This leaves only one possibility (shaded green).

Image File history File links Cross-hatching. ... Image File history File links Cross-hatching. ...

Scanning

Scanning is performed at the outset and throughout the solution. Scans need to be performed only once in between analyses. Scanning consists of two techniques:

• Cross-hatching: the scanning of rows to identify which line in a region may contain a certain numeral by a process of elimination. The process is repeated with the columns. For fastest results, the numerals are scanned in order of their frequency, from high to low. It is important to perform this process systematically, checking all of the digits 1–9.
• Counting 1–9 in regions, rows, and columns to identify missing numerals. Counting based upon the last numeral discovered may speed up the search. It also can be the case, particularly in tougher puzzles, that the best way to ascertain the value of a cell is to count in reverse—that is, by scanning the cell's region, row, and column for values it cannot be, in order to see what remains.

Advanced solvers look for "contingencies" while scanning, narrowing a numeral's location within a row, column, or region to two or three cells. When those cells lie within the same row and region, they can be used for elimination during cross-hatching and counting. Puzzles solved by scanning alone without requiring the detection of contingencies are classified as "easy"; more difficult puzzles cannot be solved by basic scanning alone.

A method for marking likely numerals in a single cell by the placing of pencil dots. To reduce the number of dots used in each cell, the marking would only be done after as many numbers as possible have been added to the puzzle by scanning. Dots are erased as their corresponding numerals are eliminated as candidates.

Image File history File links Suduko_Dots. ... Image File history File links Suduko_Dots. ...

Marking up

Scanning stops when no further numerals can be discovered, making it necessary to engage in logical analysis. One method to guide the analysis is to mark candidate numerals in the blank cells. There are two popular notations: subscripts and dots.

• In the subscript notation the candidate numerals are written in subscript in the cells. Because puzzles printed in a newspaper are too small to accommodate more than a few subscript digits of normal handwriting, solvers may create a larger copy of the puzzle.

• The second notation uses a pattern of dots in each square, where the dot position indicates a number from 1 to 9. The dot notation can be used on the original puzzle. Dexterity is required in placing the dots, since misplaced dots or inadvertent marks inevitably lead to confusion and may not be easily erased.

An alternative technique is to "mark up" the numerals that a cell cannot be. A cell will start empty and as more constraints become known, it will slowly fill until only one mark is missing. Assuming no mistakes are made and the marks can be overwritten with the value of a cell, there is no longer a need for any erasures.

Analysis

The two main approaches to analysis are "candidate elimination"^[11] and "what-if".^[12] In "candidate elimination", progress is made by successively eliminating candidate numerals from cells to leave one choice. After each answer has been achieved, another scan may be performed—usually checking to see the effect of the contingencies. In general, if entering a particular numeral prevents completion of the other necessary placements, then the numeral in question can be eliminated as a candidate. One method works by identifying "matched cell groups". For instance, if precisely two cells within a scope (a particular row, column, or region) contain the same two candidate numerals (p,q), or if precisely three cells within a scope contain the same three candidate numerals (p,q,r), these cells are said to be matched. The placement of those candidate numerals anywhere else within that same scope would make a solution impossible; therefore, those candidate numerals can be deleted from all other cells in the scope.

In the "what-if" approach (also called "guess-and-check", "bifurcation", "backtracking" and "Ariadne's thread"), a cell with two candidate numerals is selected, and a guess is made. The steps are repeated until a duplication is found or a cell is left without a possible candidate, in which case the alternative candidate must be the solution. For each cell's candidate, the question is posed: 'will entering a particular numeral prevent completion of the other placements of that numeral?' If the answer is 'yes', then that candidate can be eliminated. If the "what-if" exercises for both candidates show that either one is possible, another pair should be tried. The what-if approach requires a pencil and eraser or a good layout memory. This article or section does not cite its references or sources. ... Ariadnes thread, named for the legend of Ariadne, is the term used to describe the solving of a problem with multiple apparent means of proceeding - such as a physical maze, a logic puzzle, or an ethical dilemma - through an exhaustive application of logic to all available routes. ...

There are three kind of conflicts, which can appear during puzzle solving:

1. basic conflicts - there are only N-1 different candidates in N cell in the area
2. fish conflicts - when eliminating number from N rows/columns, it will disappear also from N+1 columns/rows.
3. unique conflicts - this pattern means multiple solutions, all numbers in the pattern exist exactly two times in every area, row and column. If there are only one candidate in the cell, any virtual candidate can be added.

Encountering any of those would indicate that the puzzle is not uniquely solvable. So, if you encounter them as a consequence of "what-if", you use your eraser and go back to try untried alternatives.

Computer solutions

There are two general approaches taken in the creation of serious Sudoku-solving programs: human solving methods and rapid-style methods. Human-style solvers will typically operate by maintaining a mark-up matrix, and search for contingencies, matched cells, and other elements that a human solver can utilize in order to determine and exclude cell values.

Many rapid-style solvers employ backtracking searches, with various pruning techniques also being used in order to help reduce the size of the search tree. The term rapid-style may be misleading: Most human-style solvers run considerably faster than a rapid-style solver, although the latter takes less time to write and is more easily adapted to larger grids. This article or section does not cite its references or sources. ...

Rapid solvers are preferred for trial-and-error puzzle-creation algorithms, which allow for testing large numbers of partial problems for validity in a short time; human-style solvers can be employed by hand-crafting puzzlesmiths for their ability to rate the challenge of a created puzzle and show the actual solving process their target audience can be expected to follow.

Although typical Sudoku puzzles (with 9×9 grid and 3×3 regions) can be solved quickly by computer, the generalization to larger grids is known to be NP-Complete. Various optimisation methods have been proposed for large grids. In complexity theory, the NP-complete problems are the most difficult problems in NP, in the sense that they are the ones most likely not to be in P. The reason is that if you could find a way to solve an NP-complete problem quickly, then you could use...

Details of computer solutions may be found on the page on the Algorithmics of Sudoku. The class of Sudoku puzzles consists of a partially completed row-column grid of cells partitioned into N regions or zones 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...

Difficulty ratings

The difficulty of a puzzle is based on the relevance and the positioning of the given numbers rather than their quantity. Surprisingly, the number of givens does not always reflect a puzzle's difficulty. Computer solvers can estimate the difficulty for a human to find the solution, based on the complexity of the solving techniques required. Some online versions offer several difficulty levels.

Most publications sort their Sudoku puzzles into four or five rating levels, although the actual cut-off points and the names of the levels themselves can vary widely. Typically, however, the titles are synonyms of "easy", "intermediate", "hard", and "challenging". An easy puzzle can be solved using only scanning; an intermediate puzzle may take markup to solve; a hard or challenging puzzle will usually take analysis.

Another approach is to rely on the experience of a group of human test solvers. Puzzles can be published with a median solving time rather than an algorithmically defined difficulty level.

Construction

Building a Sudoku puzzle can be performed by pre-determining the locations of the givens and assigning them values only as needed to make deductive progress. This technique gives the constructor greater control over the flow of puzzle solving, leading the solver along the same path the compiler used in building the puzzle. Great caution is required, however, as failing to recognize where a number can be logically deduced at any point in construction—regardless of how tortuous that logic may be—can result in an unsolvable puzzle when defining a future given contradicts what has already been built. Building a Sudoku with symmetrical givens is a simple matter of placing the undefined givens in a symmetrical pattern to begin with.

Nikoli Sudoku are hand-constructed, with the author being credited; the givens are always found in a symmetrical pattern.^[13] Dell Number Place Challenger (see Variants below) puzzles also list authors. The Sudoku puzzles printed in most UK newspapers are apparently computer-generated but employ symmetrical givens; The Guardian famously claimed that because they were hand-constructed, their puzzles would contain "imperceptible witticisms" that would be very unlikely in computer-generated Sudoku. Nikoli (ニコリ) is a Japanese publisher that specializes in games and, especially, logic puzzles. ... Wit is a form of intellectual humour, based on manipulation of concepts; a wit is someone who excels in witty remarks, typically in conversation and spontaneously, since wit carries the connotation of speed of thought. ...

Variants

A nonomino Sudoku puzzle, sometimes also known as a Jigsaw Sudoku, for instance in the Sunday Telegraph

Solution numbers in red for above puzzle

Even though the 9×9 grid with 3×3 regions is by far the most common, variations abound: sample puzzles can be 4×4 grids with 2×2 regions; 5×5 grids with pentomino regions have been published under the name Logi-5; the World Puzzle Championship has previously featured a 6×6 grid with 2×3 regions and a 7×7 grid with six heptomino regions and a disjoint region. Larger grids are also possible, with Daily SuDoku's 16×16-grid Monster SuDoku ^[14], the Times likewise offers a 12×12-grid Dodeka sudoku with 12 regions each being 4×3, Dell regularly publishing 16×16 Number Place Challenger puzzles (the 16×16 variant often uses 1 through G rather than the 0 through F used in hexadecimal), and Nikoli proffering 25×25 Sudoku the Giant behemoths. Even larger sizes, for instance 100×100,^[15] have been claimed. Image File history File links Nonomino_Sudoku. ... Image File history File links Nonomino_Sudoku. ... It has been suggested that this article or section be merged with Picture puzzle. ... This article deals with The Daily Telegraph in Britain, see The Daily Telegraph (Australia) for the Australian publication The Daily Telegraph is a British broadsheet newspaper founded in 1855. ... Image File history File links Nonomino_Sudoku_solution. ... Image File history File links Nonomino_Sudoku_solution. ... A pentomino is a polyomino composed of five (Greek πέντε / pente) congruent squares, connected orthogonally. ... The World Puzzle Championship is an annual international puzzle competition run by the World Puzzle Federation. ... ... In mathematics and computer science, base-16, hexadecimal, or simply hex, is a numeral system with a radix or base of 16, usually written using the symbols 0–9 and A–F or a–f. ...

Another common variant is for additional restrictions to be enforced on the placement of numbers beyond the usual row, column, and region requirements. Often the restriction takes the form of an extra "dimension"; the most common is for the numbers in the main diagonals of the grid to also be required to be unique. The aforementioned Number Place Challenger puzzles are all of this variant, as are the Sudoku X puzzles in the Daily Mail, which use 6×6 grids. The Daily Mail is a British newspaper, a tabloid, first published in 1896. ...

Puzzles constructed from multiple Sudoku grids are common. Five 9×9 grids which overlap at the corner regions in the shape of a quincunx is known in Japan as Gattai 5 (five merged) Sudoku. In The Times, The Age and The Sydney Morning Herald this form of puzzle is known as Samurai SuDoku.^[16] Puzzles with twenty or more overlapping grids are not uncommon in some Japanese publications. Often, no givens are to be found in overlapping regions. Sequential grids, as opposed to overlapping, are also published, with values in specific locations in grids needing to be transferred to others. A quincunx is the arrangement of five units in the pattern corresponding to the five-spot on dice, playing cards, or dominoes. ... The Times is a national newspaper published daily in the United Kingdom since 1785, and under its current name since 1788. ... The Age is a broadsheet daily newspaper, which has been published in Melbourne, Australia since 1854. ... This article or section does not cite its references or sources. ...

Alphabetical variations have also emerged; there is no functional difference in the puzzle unless the letters spell something. Some variants, such as in the TV Guide, include a word reading along a main diagonal, row, or column once solved; determining the word in advance can be viewed as a solving aid. The Code Doku^[17] devised by Steve Schaefer has an entire sentence embedded into the puzzle; the Super Wordoku^[18] from Top Notch embeds two 9-letter words, one on each diagonal. It is debatable whether these are true Sudoku puzzles: although they purportedly have a single linguistically valid solution, they cannot necessarily be solved entirely by logic, requiring the solver to determine the embedded words. Top Notch claims this as a feature designed to defeat solving programs. TV Guide is the name of two North American weekly magazines about television programming, one in the United States and one in Canada. ...

There is also a Sudoku version of the Rubik's Cube, named Sudokube. Variations of Rubiks Cubes (from left to right: Rubiks Revenge, Rubiks Cube, Professors Cube, & Pocket Cube) The Rubiks Cube is a mechanical puzzle invented in 1974 by the Hungarian sculptor and professor of architecture Ernő Rubik. ... There are very few or no other articles that link to this one. ...

Here are some of the more notable single-instance variations:

• A three-dimensional Sudoku puzzle was invented by Dion Church and published in the Daily Telegraph in May 2005.
• A book of 3 dimensional puzzles was released by Richard John on the 3rd of November 2006. The book "Sudoku-Stak[1]. The Complete Introduction Book 1" is believed to be the first book of 3D puzzles.
• The 2005 U.S. Puzzle Championship includes a variant called Digital Number Place: rather than givens, most cells contain a partial given—a segment of a number, with the numbers drawn as if part of a seven-segment display.
• The online journal Speculative Grammarian has published a trio of linguistics-themed Sudoku-like puzzles called LingDoku, which require the solver to solve for two or more variables at once, including a simple 3×3 puzzle,^[19], a slightly more complicated 4x4 puzzle,^[20] and a Samurai-style puzzle with 3 overlapping 3×3 grids.^[21]

This article deals with The Daily Telegraph in Britain, see The Daily Telegraph (Australia) for the Australian publication The Daily Telegraph is a British broadsheet newspaper founded in 1855. ... A seven-segment display (abbreviation: 7-seg(ment) display), less commonly known as a seven-segment indicator, is a form of display device that is an alternative to the more complex dot-matrix displays. ... Speculative Grammarian is the self-described premier scholarly journal featuring research in the neglected field of satirical linguistics. ...

An example of a Hexudoku.

A Hexudoku (also spelled Hexadoku) is a variant of the game Sudoku, which uses a grid of 16x16 squares instead of 9x9. The name originates from the contraction of the Greek-, and Latin prefixes hexa-deca, which means 16, and the word sudoku. Image File history File links Hexudoku. ... Image File history File links Hexudoku. ...

Similar to Sudoku, the goal of the game is to complete a not-completely filled grid, such that each row, each column, and each of the 16 marked 4x4 squares contains each number between 1 and 16 exactly once. With 256 squares, the hexudoku has more than 3 times as many squares as the regular sudoku.

Instead of the numbers 1 to 16, sometimes the hexadecimal digits 0-9, a-f are used, or a variant starting at 1: 1-9, a-g. Also a letter-only variant is sometimes used.

Mathematics of Sudoku

Main article: Mathematics of Sudoku

A completed Sudoku grid is a special type of Latin square with the additional property of no repeated values in any 3×3 block. The number of classic 9×9 Sudoku solution grids was shown in 2005 by Bertram Felgenhauer and Frazer Jarvis to be 6,670,903,752,021,072,936,960 ^[22] (sequence A107739 in OEIS) : this is roughly 0.00012% the number of 9×9 Latin squares. Various other grid sizes have also been enumerated—see the main article for details. The number of essentially different solutions, when symmetries such as rotation, reflection and relabelling are taken into account, was shown by Ed Russell and Frazer Jarvis to be just 5,472,730,538 ^[23] (sequence A109741 in OEIS). Both results have been confirmed by independent authors.^{[citation needed]} 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... A Latin square is an n × n table filled with n different symbols in such a way that each symbol occurs exactly once in each row and exactly once in each column. ... The On-Line Encyclopedia of Integer Sequences (OEIS) is an extensive searchable database of integer sequences, freely available on the Web. ... 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... The On-Line Encyclopedia of Integer Sequences (OEIS) is an extensive searchable database of integer sequences, freely available on the Web. ...

The maximum number of givens provided while still not rendering the solution unique is four short of a full grid; if two instances of two numbers each are missing and the cells they are to occupy form the corners of an orthogonal rectangle, and exactly two of these cells are within one region, there are two ways the numbers can be assigned. Since this applies to Latin squares in general, most variants of Sudoku have the same maximum. The inverse problem—the fewest givens that render a solution unique—is unsolved, although the lowest number yet found for the standard variation without a symmetry constraint is 17, a number of which have been found by Japanese puzzle enthusiasts,^{[24] [25]} and 18 with the givens in rotationally symmetric cells. This article lists some currently unsolved problems in mathematics. ...

History

Page from La France newspaper, July 6, 1895

Main article: History of Sudoku

Number puzzles first appeared in newspapers in the late 19th century, when French puzzle setters began experimenting with removing numbers from magic squares. Le Siècle, a Paris-based daily, published a partially completed 9×9 magic square with 3×3 sub-squares in 1892.^[26] It was not a Sudoku because it contained double-digit numbers and required arithmetic rather than logic to solve, but it shared key characteristics: each row, column and sub-square added up to the same number. Image File history File links Download high resolution version (502x635, 315 KB) Summary I copied this image from a copy of the French newspaper La France, dated June 1895. ... Image File history File links Download high resolution version (502x635, 315 KB) Summary I copied this image from a copy of the French newspaper La France, dated June 1895. ... Sudoku is a logic game made up of a square divided into 81 smaller squares. ... In mathematics, magic squares consist of a number of integers arranged in the form of a square in such a way that the sum of the numbers in every row, column and diagonal are the same. ...

Within three years Le Siècle's rival, La France, refined the puzzle so that it was almost a modern Sudoku. It simplified the 9×9 magic square puzzle so that each row and column contained only the numbers 1–9, but did not mark the sub-squares. Although they are unmarked, each 3×3 sub-square does indeed comprise the numbers 1–9. However, the puzzle cannot be considered the first Sudoku because, under modern rules, it has two solutions. The puzzle setter ensured a unique solution by requiring 1–9 to appear in both diagonals.

These weekly puzzles were a feature of newspaper titles including L'Echo de Paris for about a decade but disappeared about the time of the First World War.^[27] Ypres, 1917, in the vicinity of the Battle of Passchendaele. ...

According to Will Shortz, the modern Sudoku was most likely designed anonymously by Howard Garns, a 74-year-old retired architect and freelance puzzle constructor, and first published in 1979 by Dell Magazines as Number Place (the earliest known examples of modern Sudoku). Garns's name was always present on the list of contributors in issues of Dell Pencil Puzzles and Word Games that included Number Place, and was always absent from issues that did not.^[10] Sadly, he died in 1989 before getting a chance to see his creation as a worldwide phenomenon.^[10] Will Shortz (b. ... Dell Magazines is a company founded by George T. Delacorte Jr. ...

The puzzle was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984^[10] as Suuji wa dokushin ni kagiru (数字は独身に限る, Suuji wa dokushin ni kagiru^?), which can be translated as "the numbers must be single" or "the numbers must occur only once." At a later date, the name was abbreviated to Sudoku by Maki Kaji (鍜治 真起, Kaji Maki^?), taking only the first kanji of compound words to form a shorter version.^[10] In 1986, Nikoli introduced two innovations: the number of givens was restricted to no more than 32^{[citation needed]}, and puzzles became "symmetrical" (meaning the givens were distributed in rotationally symmetric cells).^[9] It is now published in mainstream Japanese periodicals, such as the Asahi Shimbun. Nikoli (ニコリ) is a Japanese publisher that specializes in games and, especially, logic puzzles. ... Japanese writing Kanji Kana Hiragana Katakana Hentaigana Manyōgana Uses Furigana Okurigana Rōmaji Kanji (Japanese:  ) are the Chinese characters that are used in the modern Japanese logographic writing system along with hiragana (平仮名), katakana (片仮名), and the Arabic numerals. ... Asahi-OSAKA office Asahi is a common name in Japan, for other uses see Asahi. ...

Popularity in the media

This article or section deals primarily with the United Kingdom and does not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page.

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.^[28] 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). Image File history File links Gnome-globe. ... Wayne Gould (born 1945 in New Zealand) is a retired Hong Kong judge, most recently known for helping to popularize sudoku puzzles in the United Kingdom. ... The crossword is the most common variety of word puzzle in the world. ... The Times is a national newspaper published daily in the United Kingdom since 1785, and under its current name since 1788. ... November 12 is the 316th day of the year (317th in leap years) in the Gregorian Calendar, with 49 days remaining. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

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 ^[29]). 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. June 20 is the 171st day of the year (172nd in leap years) in the Gregorian Calendar, with 194 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... Channel 4 is a public-service television broadcaster in the United Kingdom (see British television). ... This article or section is not written in the formal tone expected of an encyclopedia article. ... August 2 is the 214th day of the year in the Gregorian Calendar (215th in leap years), with 151 days remaining. ... Current Radio Times logo Radio Times is the BBCs weekly television and radio programme listings magazine. ...

The world's first live TV Sudoku show, 1 July 2005, Sky One.

The world's first live TV Sudoku show, Sudoku Live, was 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. The audience at home was in a separate interactive competition. Image File history File links SudokuLive2. ... Image File history File links SudokuLive2. ... July 1 is the 182nd day of the year (183rd in leap years) in the Gregorian Calendar, with 183 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... July 1 is the 182nd day of the year (183rd in leap years) in the Gregorian Calendar, with 183 days remaining. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... Sky One is one of British Sky Broadcastings entertainment channels in the United Kingdom and Republic of Ireland. ... Carol Jean Vorderman MBE (born 24 December 1960), is a British television personality best known for being a long-standing co-presenter of Channel 4 game show Countdown. ...

Later in 2005, the BBC launched SUDO-Q, a game show that combines Sudoku with general knowledge. However, it uses only 4x4 and 6x6 puzzles. The British Broadcasting Corporation, usually known as the BBC (and also informally known as the Beeb or Auntie) is one of the largest broadcasting corporations in the world in terms of audience numbers, employing 26,000 staff in the UK alone and with a budget of more than £4 billion. ... SUDO-Q is BBC quiz show based on a mix of the number puzzle Sudoku and general knowledge questions. ... A game show involves members of the public or celebrities, sometimes as part of a team, playing a game, perhaps involving answering quiz questions, for points or prizes. ...

Early in 2006, Sudoku was brought to a younger generation for the DS, a handheld game console developed and manufactured by Nintendo. Sudoku made a humble feature in Brain Age: Train Your Brain in Minutes a Day!, an educational game developed by Japanese neuroscientist Ryūta Kawashima. With the popularity of sudoku rising, a game called Sudoku Gridmaster was released focusing solely on the logic-based numerical puzzle. At approximately the same time, Sudoku Mania was released. However, compared to the success of the previous two titles, Sudoku Mania received generally negative reviews from gaming critics and gamers. 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... The Nintendo DS, sometimes abbreviated NDS or DS, is a handheld game console developed and manufactured by Nintendo, and first released in 2004. ... One of the first handheld game consoles, Ball was the first product in the Game & Watch series. ... It has been suggested that Multiplayer game be merged into this article or section. ... Nintendo Company, Limited (任天堂 or ニンテンドー Nintendō; NASDAQ: NTDOY, TYO: 7974 usually referred to as simply Nintendo, or Big N ) is a multinational corporation founded on September 23, 1889[1] in Kyoto, Japan by Fusajiro Yamauchi to produce handmade hanafuda cards. ... Drawing of the cells in the chicken cerebellum by S. Ramón y Cajal Neuroscience is a field that is devoted to the scientific study of the nervous system. ... RyÅ«ta Kawashima RyÅ«ta Kawashima ) (born May 23, 1959) is the Japanese neuroscientist who was made famous because of his appearance in the Nintendo DS game Brain Age: Train Your Brain in Minutes a Day. ... Sudoku Gridmaster is a puzzle game for the Nintendo DS, scheduled to released on March 23, 2006 in Japan and June 26, 2006 in the United States. ... Logic, from Classical Greek λόγος logos (the word), is the study of patterns found in reasoning. ... Gamer is a term used to describe a person who plays games. ...

Sudoku is now also a very popular part of the games available for mobile phones. Gameloft, Guardian Unlimited, World Sudoku League and Playcom are some of the distributors.

Competitions

• The first world championship was held in Lucca, Italy from 10 to 12 March 2006;^[30] it was won by Jana Tylová, a 31-year-old accountant from the Czech Republic. The competition included numerous variants.^[31]
• The second world championship will be held in Prague from March 28 to April 1, 2007;^[32]

Lucca is a city in Tuscany, northern central Italy, situated on the river Serchio in a fertile plain near (but not on) the Ligurian Sea. ... This article or section does not cite its references or sources. ...

See also

• List of Nikoli puzzle types
• List of Sudoku terms and jargon
• Killer sudoku
• Kakuro
• Paint by numbers
• Roxdoku (3D variant)

Mathematics This is a list of major puzzles published by Nikoli. ... A Sudoku puzzle (image hyperlinked to solution) This is a list of Sudoku terms and jargon. ... Killer sudoku (also killer su doku, sumdoku, sum doku or samunamupure) is a puzzle that combines elements of sudoku and kakuro. ... Easy Cross Sums puzzle The Cross Sums is a very common type of logic puzzle that is often referred to as a mathematical transliteration of the crossword. ... Example of a paint by numbers puzzle being solved. ...

• Mathematics of Sudoku
• Algorithmics of sudoku
• Latin square
• Logic puzzle

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... The class of Sudoku puzzles consists of a partially completed row-column grid of cells partitioned into N regions or zones 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... A Latin square is an n × n table filled with n different symbols in such a way that each symbol occurs exactly once in each row and exactly once in each column. ... A logic puzzle is a puzzle deriving from the mathematics field of deduction. ...

References

2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... October 6 is the 279th day of the year (280th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... October 6 is the 279th day of the year (280th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... October 6 is the 279th day of the year (280th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... October 6 is the 279th day of the year (280th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... October 6 is the 279th day of the year (280th in leap years). ... Speculative Grammarian is the self-described premier scholarly journal featuring research in the neglected field of satirical linguistics. ... Speculative Grammarian is the self-described premier scholarly journal featuring research in the neglected field of satirical linguistics. ... Speculative Grammarian is the self-described premier scholarly journal featuring research in the neglected field of satirical linguistics. ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... September 16 is the 259th day of the year (260th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... September 16 is the 259th day of the year (260th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... September 16 is the 259th day of the year (260th in leap years). ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... This article is about the date September 11 in general. ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... November 15 is the 319th day of the year (320th in leap years) in the Gregorian Calendar, with 46 days remaining. ...

External links

• Sudoku at the Open Directory Project – An active listing of Sudoku links.

The Open Directory Project (ODP), also known as dmoz (from directory. ...