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How to Play Sudoku: Step by Step Puzzle Solution

Sudoku is a very interesting puzzle. It is necessary to arrange the numbers from 1 to 9 in the field in such a way that each row, column and block of 3 x 3 cells contains all the numbers, and at the same time they should not be repeated. Let's consider step-by-step instructions on how to play Sudoku, basic methods and solution strategy.

Solution algorithm: from simple to complex

The algorithm for solving the Sudoku online mind game is quite simple: you need to repeat the following steps until the problem is completely solved. Gradually move from the simplest steps to the more complex ones, when the former no longer allow you to open a cell or exclude a candidate.

Single candidates

First of all, for a more visual explanation of how to play Sudoku online, we will introduce a numbering system for the blocks and cells of the field. Both cells and blocks are numbered from top to bottom and left to right.

Let's start looking at our field. First you need to find single candidates for a place in the cell. They can be hidden or explicit. Consider the possible candidates for the sixth block: we see that only one of the five free cells contains a unique number, therefore, the four can be safely entered into the fourth cell. Considering this block further, we can conclude that the second cell should contain the number 8, since after the exclusion of the four, the eight in the block is not found anywhere else. With the same justification, we put the number 5.

Further, we consider each row, column or block for the presence of hidden or explicit single candidates, taking into account the previously entered numbers, and enter them in the field. Review all possible options carefully. Looking at the central cell of the fifth block, we find that there can be no more options besides the number 9 - this is an obvious single candidate for this cell. The nine can be crossed out from the rest of the cells of this block, after which the rest of the numbers can be easily entered. Using the same method, we go through the cells of other blocks.

How to spot hidden and overt naked couples

Having entered the necessary numbers in the fourth block, let us return to the empty cells of the sixth block: it is obvious that the number 6 should be in the third cell, and 9 in the ninth.

Naked couple concept is present only in free Sudoku game. The rules for their detection are as follows: if in two cells of one block, row or column there is an identical pair of candidates (and only this pair!), Then the rest of the cells of the group cannot have them. Let us explain this using the example of the eighth block. Putting possible candidates in each cell, we find an explicit “naked pair”. The numbers 1 and 3 are present in the second and fifth cells of this block, and there and there are only 2 candidates each, therefore, they can be safely excluded from the rest of the cells.

Completing the puzzle

If you have learned the lesson on how to play Sudoku and followed the above instructions step by step, then you should get something like the following picture as in this field: Here you can find single candidates: one in the seventh cell of the ninth block and two in the fourth cell third block. Try to solve the puzzle to the end. Now compare the result with the correct solution.

Happened? Congratulations, this means that you have successfully learned the lessons of how to play Sudoku and learned how to solve the simplest puzzles. There are many varieties of this game: Sudoku of different sizes, Sudoku with additional areas and additional conditions. The playing field can vary from 4 x 4 to 25 x 25 cells.

You may come across a puzzle in which numbers cannot be repeated in an additional area, for example, diagonally. Start with simple options and gradually move on to more complex ones, because experience comes with training.

Useful Resources:

Sudoku on guard for your brain!

Online Sudoku game