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BackgroundThe name SuDoku is Japanese and can roughly be translated as "single number". The game SuDoku has been popular in Japan since the mid 1980s but has only recently become popular in Europe, triggered primarily by the publishing of SuDoku puzzles in British newspapers starting November 2004. The rules are simple, fill a 9 by 9 cell grid such that the numbers 1 to 9 appear once only in each row, column and block. A block is a 3 by 3 grid of which there are 9 in the main grid. There are apparently 6 trillion possible solutions. To be uniquely solvable a puzzle must have at least 17 initial numbers. The degree of difficulty of a puzzle depends on the number of initial numbers given and their distribution. As a rule of thumb, 24 initial numbers constitute a very difficult puzzle, whereas 48 numbers constitute a simple puzzle. Although the Japanese have given the name to the puzzle, its roots go back to the Swiss Mathematician Leonhard Euler whose theory of "Latin Squares" which he developed in 1783 shortly before his death, is considered to be the forerunner of SuDoku. Comments or suggestions to Support@sudoku-solutions.com |