Background
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| The 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 the rest of the world, triggered
primarily by the publishing of SuDoku puzzles in British newspapers starting
November 2004. |
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| 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. |
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Rules
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| 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 box. A box is a 3 by 3 grid of which there
are 9 in the main grid. |
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| 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. |
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| A valid
Sudoku has a unique solution which can be found using an array of solving
techniques without the need to guess. |
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|
Solving
Techiques
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| A large
number of solving techniques have been developed. Here is a non-exhaustive
list grouped by difficulty level. Alternative names for solving techiques are
given in brackets. Click on the link where present for more detailed
information on the solving technique. |
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