SUDOKU
What is SuDoKu?
Sudoku is a logic-based number-placement puzzle. The objective is to fill a 9×9 grid so that each column, each row, and each of the nine 3×3 boxes (also called blocks or regions) contains the digits from 1 to 9 only one time each. The puzzle setter provides a partially completed grid.
Introduction
The name Sudoku(数独) is short for “数字は独身に限る” which is read, “Sūji wa dokushin ni kagiru”, meaning “the numbers must be single”, or “the numbers must occur only once”. The name is a trademark of puzzle publisher Nikoli Co. Ltd. in Japan. In Japanese, the word is pronounced IPA: [sɯːdokɯ]; in English, it is usually IPA: /səˈdoʊkuː/. Other Japanese publishers refer to the puzzle as Number Place, the original U.S. title, or as “Nanpure”(ナンプレ) for short. Some publishers spell the title as “Su Doku”.
The numerals in Sudoku puzzles are used for convenience; arithmetic relationships between numerals are irrelevant. Any set of distinct symbols will do, such as letters, shapes, or colours. In fact, ESPN published Sudoku puzzles substituting the positions on a baseball field for the numbers 1 through 9, while Viz magazine has published a Doctor Who version of the game, using images of the television series’ first nine leading actors in place of the numerals. Dell Magazines, the puzzle’s originator, has been using numerals for Number Place in its magazines since they first published it in 1979.
History
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. 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.
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.
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 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 Suuji wa dokushin ni kagiru (数字は独身に限る, Suuji wa dokushin ni kagiru?), which can be translated as “the digits must be single” or “the digits are limited to one occurrence.” 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.[6] 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.
Resource: http://en.wikipedia.org/wiki/Sudoku
