Sudoku is a very interesting puzzle. It is necessary to arrange the numbers from 1 to 9 in the field so that each row, column and block 3 x 3 cells contain all the numbers, and at the same time they should not be repeated. Consider the step-by-step instructions on how to play Sudoku, the basic methods and solution strategy.
Solution Algorithm: From Simple to Complex
The algorithm for solving the Sudoku mind game is quite simple: you need to repeat the following steps until the problem is completely solved. Gradually move from the simplest to the more complex steps, when the first ones 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, we will introduce a numbering system for blocks and field cells. Both cells and blocks are numbered from top to bottom and from 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 of the sixth block: we see that only one of the five free cells has a unique number, therefore, the four can be safely entered into the fourth cell. Considering this block further, we can conclude: in the second cell there should be a number 8, since after the exclusion of the four, the eight in the block does not appear anywhere else. With the same justification we put the number 5.
Next, we consider each row, column or block for the presence of hidden or explicit single candidates, taking into account the numbers put down earlier, and enter them in the field.
Carefully review all possible options. Looking at the central cell of the fifth block, we find that in addition to the number 9 there can be no more options - this is a clear single candidate for this cell. The nine can be deleted from the remaining cells of this block, after which the remaining numbers can be easily entered. Using the same method, we go through the cells of other blocks.
How to detect hidden and explicit "naked couples"
Having put the necessary numbers in the fourth block, we return to the blank cells of the sixth block: it is obvious that the number 6 should be in the third cell, and 9 in the ninth.
The concept of “naked couple” is present only in the game of sudoku. The rules for their detection are the following: if in two cells of the same block, row or column there is an identical pair of candidates (and only this pair!), Then the rest of the cells in the group cannot have them. Let us explain this with the example of the eighth block. Having put possible candidates in each cell, we find an explicit “bare 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 remaining cells.
Puzzle completion
If you learned a lesson on how to play Sudoku and followed the steps above step by step, then you should get something like this in this field:
Here you can find single candidates: a unit in the seventh cell of the ninth block and a deuce in the fourth cell of the third block. Try to solve the puzzle to the end. Now compare the result with the correct solution.
Happened? Congratulations, because this means that you have successfully learned the lessons of how to play Sudoku and learned how to solve simple 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 the 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.