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International Sudoku Day. Sudoku rules

International Sudoku Day is celebrated on September 9th. Sudoku is a number puzzle in the form of a 9th order Latin square. It is actively published by newspapers and magazines from around the world, and collections of Sudoku are published in huge circulations. There are also desktop, computer and mobile game options.

The prototype of the modern japanese free Sudoku puzzles originated in ancient China. These were the so-called magic squares. In Europe, something similar was solved in the 18th century, when the blind Swiss mathematician Leonard Euler found out that in a 9x9 matrix, each row and column can be filled with numbers from 1 to 9 without repetition. It was only in 1979 that Sudoku made its way to the pages of the American magazine Math Puzzles and Logic Problems under the name Number Place, which is still used in the United States. But only 15 years ago Sudoku really conquered the world. Puzzles began to appear in English newspapers, and in 2005, Japanese magazines. In the same year, American scientists Bertram Felgenhoer and Frazer Jarvis calculated the number of possible combinations of numbers for 9x9 squares Sudoku online. Their number was 6 670 903 752 021 072 936 960 different combinations. According to the results of 8 World Sudoku Championships, Thomas Snyder (USA) and Jan Mrozowski (Poland) became the best in the individual standings three times each.

Today, International Sudoku Day serves as an excuse to enjoy games related to finding words and numbers, choosing numerical combinations, from puzzles to crossword puzzles to Sudoku itself.

Sudoku rules

The playing field is a 9 × 9 square, divided into smaller squares with a side of 3 cells. Thus, the entire playing field consists of 81 cells. At the beginning of the game, they contain some numbers (from 1 to 9), called hints. The player is required to fill the empty cells with numbers from 1 to 9 so that in each row, in each column and in each small 3 × 3 square, each number occurs only once.

The difficulty of Sudoku depends on the number of initially filled cells and on the methods that need to be used to solve it. The simplest ones are solved deductively: there is always at least one cell where only one number fits. Some puzzles can be solved in minutes, others can take hours.

A correctly formed puzzle has only one solution. Nevertheless, on some sites on the Internet, under the guise of complicated puzzles, the user is offered Sudoku options with several solutions, as well as branches of the solution itself.

Related Resources:

How to make a Sudoku?

Is it useful to solve Sudoku?

What are the benefits of logic games?


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