How often on travel do you get tired of looking out the window and want to occupy your mind? In such a situation, Sudoku will come to the rescue. This is a great way to entertain the mind and give it a little workout. So, how to play sudoku?

### How to play sudoku

Sudoku’s roots stem from an 18th-century game, made by Swiss mathematician called “Latin Squares” (according to this article from the Economist), and some of the first puzzles that appeared in newspapers were published in France in 1895. But the modern Sudoku game, as we know it today, was created by Howard Garns, an independent puzzle developer from Connersville, Indiana, USA, in 1979, when it was published in Dell Pencil Puzzles and Word Games ” This puzzle was known as the “Number Place” because it required placing the missing numbers in empty spaces on a 9 x 9 grid. The game first appeared in Japan in 1984, where it was given the name Sudoku, which is a shortened version of a longer expression in Japanese, Sūji wa dokushin ni kagiru. This expression means “numbers are limited to one location.” Sudoku is still very popular in Japan, where more than 600,000 magazines are sold every month. Do you already know how to solve simple sudoku? This is an addictive process that forces you to use logic and keep the decision algorithm in your head. If everything is done methodically, then solving complex sudoku is not so difficult, the main thing is to adhere to the correct sudoku strategies. It will take more time, but in fact the process is almost the same. The main thing is to follow the sudoku rules and find the point to which you need to return. Here are some sudoku tips:

I usually go from 1 to 9 in easy sudoku and look where there is a cell in which there can definitely be only one of the numbers. Then I repeat this action again, because after substituting one digit, the “next move” appears. These steps are repeated until this method works. Over the years, sudoku has developed many approaches to solving. We offer several methods, from simple to complex.

**Singles** (the only options) are determined after the exclusion of numbers that are already inscribed in rows, columns or areas. If by elimination it is possible to reveal the only possible number, the single is called obvious. Simple sudoku is solved in this way.

The numbers 1, 5, 6, 9 are excluded – they are in a row.

2, 3, 8 – located in the column.

6, 7, 8 – may be present in the area.

The only candidate in cell E6 remains 4.

**Hidden singles **(How to play sudoku)

The number can be entered into the cell if another arrangement in the group is not possible. This probability can be determined after placing candidates and identifying a number that is not repeated anywhere else.

In the seventh and ninth row, 8 is inscribed initially.

8 is in column A.

In the lower left area, you can enter 8 only in one cell – B8, so the remaining candidates need to be excluded.

#### Difficult sudoku

How to play sudoku which is difficult? Many people wonder how to solve sudoku, are there standard methods and strategies. As in any logical puzzle is. The simplest of them we already examined. To go to a higher level, you need to have a greater margin of time, perseverance, patience. To solve the puzzle, you have to make assumptions and, possibly, get the wrong result, returning to the place of choice. Essentially hard sudoku – this is how to solve a problem using an algorithm.

Consider several popular techniques used by professionals in the following example.

**Open Pairs Method**

Take this example. First, fill in all the obvious options.

To clear the field further, you need to find open pairs that allow you to exclude the numbers in them from other cells in the block and rows. In the example, such pairs are 4 and 9 from the third line. They demonstrate how to solve complex sudoku. Their combination suggests that only 4 or 9 can be put in these cells. This conclusion is made on the basis of Sudoku rules.

From the cells highlighted in green, you can remove the values in the blue cells and thereby reduce the number of options. Moreover, the combination 1249 located in the first row is called by analogy the “open four”. You can also meet the “open threes.” Such actions entail the appearance of other open pairs, for example 1 and 2 in the top line, which also make it possible to narrow down the circle of combinations. In parallel, we put down the first square 7 in the circled cell, since the five in this row will in any case be located in the lower block.

**Hidden Pairs** / Three / Fours Method This method is the opposite of open combinations. Its essence lies in the fact that it is necessary to find cells in which the numbers within the square / line are repeated that are not found in other cells. How does this help solve sudoku? Reception allows you to cross off the remaining numbers, as they serve as the background and cannot be affixed to the selected cells. This strategy has several other names, for example, “Cell is not infinite” “Secret becomes apparent.” The names themselves explain the essence of the method and compliance with the rule, talking about the possibility to put down a single number. An example is blue-stained cells. Numbers 4 and 7 are found exclusively in these cells, so the rest can be safely removed. The “conjugation system” acts in a similar way when it is possible to exclude from the cells of a block / row / column values several times occurring in an adjacent or conjugated one.

“**Cross Exclusion**”

The principle of how to solve sudoku is based on the ability to analyze and compare. Another way to exclude options is to have a number in two columns or rows that intersect. In our example, such a situation did not occur, therefore, consider another. The picture shows that the “deuce” occurs in the second and third middle block once, and the combinations are connected and mutually exclusive. Based on this data, the number 2 can be deleted from other cells in the specified columns. Can also be applied to three and four lines. The complexity of the method lies in the difficulties of visualizing and identifying relationships. Reduction method. As a result of each action, the number of options in the cells is reduced and the solution is reduced to the Loner method. This process can be called an abbreviation and distinguished in a separate method, since it involves a thorough analysis of all rows, columnsvand small squares with the sequential exclusion of options. In the end, we come to a single solution.

“**Color Method**”

This strategy does not differ much from that described, and consists in the color indication of cells or numbers. The method helps to visualize the entire course of the solution, however, it is not suitable for everyone. Some colors knock down and interfere with focus. In order to correctly use the gamma, you need to choose two or three colors and paint the same options in them in different blocks / lines, as well as the controversial cells. To figure out how to solve sudoku, it is better to arm yourself with a pen and paper. This approach will allow you to train your head, in contrast to the use of electronic algorithms with the presence of tips. There are many other algorithms. For example, the “Trial and error” method, when a trial version is selected from two or three possible ones and the entire chain is checked. The disadvantage of this technique is the need to use a computer, since it is not so easy to return to the original version on a piece of paper.

Now you do know how to play sudoku!

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