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Introduction
Sudoku, sometimes spelled Su Doku, is a placement puzzle, also known as Number Place in the United States. The aim of the puzzle
is to enter a numeral from 1 through 9 in each cell of a grid, most frequently a 9×9 grid made up of 3×3 subgrids (called "regions"), starting with
various numerals given in some cells (the "givens"). Each row, column and region must contain only one instance of each numeral. Completing the puzzle
requires patience and modest logical ability (although some puzzles can be very difficult). Its classic grid layout is reminiscent of other newspaper
puzzles like crosswords and chess problems. First published in the United States, Sudoku initially became popular in Japan in 1986 and attained
international popularity in 2005.
The word Sudoku means "single number" in Japanese. The numerals in Sudoku puzzles are used for convenience; arithmetic relationships
between numerals are not important. Any set of distinct symbols will do; letters, shapes, or colours may be used without altering the rules.
History
The puzzle was first published in New York in the late 1970s by the specialist puzzle publisher Dell Magazines in its magazine Math Puzzles and
Logic Problems, under the title Number Place. The person who designed the puzzle and composed the first of its kind is not recorded, but it was
probably Walter Mackey, one of Dell's puzzle constructors. The puzzle was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984
as "Suji wa dokushin ni kagiru", which can be translated as "the numbers must be single" or "the numbers must occur only once". The puzzle was named
by Kaji Maki, the president of Nikoli. At a later date, the name was abbreviated to Sudoku (pronounced sue-do-koo; su = number, doku = single);
it is a common practice in Japanese to take only the first kanji of compound words to form a shorter version. In 1986, Nikoli introduced two
innovations which guaranteed the popularity of the puzzle: the number of givens was restricted to no more than 30 and puzzles became "symmetrical"
(meaning the givens were distributed in rotationally symmetric cells).
In 1989, Loadstar/Softdisk Publishing published DigitHunt on the Commodore 64, which was apparently the first home computer version of Sudoku.
At least one publisher still uses that title.
This article is licensed under the GNU Free Documentation License.
It uses material from
the Wikipedia article "Sudoku".
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