History of Sudoku
Number puzzles appeared in newspapers in the late 19th century, when French puzzle setters began experimenting with removing numbers from magic squares. Le Siecle, a Paris-based daily, published a partially completed 9x9 magic square with 3x3 sub-squares on November 19, 1892. 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.
On July 6, 1895, Le Siecle's rival, La France, refined the puzzle so that it was almost a modern Sudoku. It simplified the 9x9 magic square puzzle so that each row, column and broken diagonals contained only the numbers 1-9, but did not mark the sub-squares. Although they are unmarked, each 3x3 sub-square does indeed comprise the numbers 1-9 and the additional constraint on the broken diagonals leads to only one solution.
These weekly puzzles were a feature of French newspapers such as L'Echo de Paris for about a decade but disappeared about the time of World War
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 from Connersville, Indiana, 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. He died in 1989 before getting a chance to see his creation as a worldwide phenomenon. It is unclear if Garns was familiar with any of the French newspapers listed above.
The puzzle was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984 as Suji wa dokushin ni kagiru, which also can be translated as "the digits must be single" or "the digits are limited to one occurrence." (In Japanese, dokushin means an "unmarried person".) At a later date, the name was abbreviated to Sudoku by Maki Kaji, taking only the first kanji of compound words to form a shorter version. Sudoku is a registered trademark in Japan and the puzzle is generally referred to as Number Place. In 1986, Nikoli introduced two innovations: the number of givens was restricted to no more than 32, and puzzles became "symmetrical" (meaning the givens were distributed in rotationally symmetric cells). It is now published in mainstream Japanese periodicals, such as the Asahi Shimbun.
The Times of London began featuring Sudoku in 2004.
