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**How to solve classic Sudoku of any difficulty?**

The first Sudoku in life almost always seems difficult, and this circumstance discourages some from solving such puzzles. If you understand the rules of the game and choose a Sudoku that matches your experience and knowledge, difficulties will remain in the past, and you can move on to difficult and very difficult Sudoku.

Some patterns can be identified independently, and we will introduce you to the basic principles. Sudoku connoisseurs have already developed effective approaches to solving the game, and you can choose the ones that suit you at a particular stage of mastering the game. But first you need to agree on the terminology.

**Terminology Sudoku**

- Cell. The main element of very easy Sudoku. All cells must be filled with numbers from 1 to 9. Each of the cells is simultaneously in a row, column and area.

- Group. There are several groups: a row - 9 horizontal cells; column - 9 vertical cells; area - a small square measuring 3 × 3 cells. Each Sudoku has 9 areas.

Segment. Part of the area - 3 horizontal or vertical cells. Each area has 6 segments - parts of a large row or column.

- Candidates. The numbers that can be inscribed in the cage (in the figure - in small print). When all but one of the candidates have been deleted, the number can be entered “on a permanent basis”. Two candidates - a couple, three - a trio, four - a quartet.

**Ways to solve sudoku**

Over the years, Sudoku has developed many approaches to solving. We offer several methods, from simple to complex.

**1. Singles (only options)**

Singles are determined after excluding numbers that are already inscribed in rows, columns, or areas. This is the way to solve simple Sudoku online.

**1.1. Obvious singles**

If only one possible number can be identified by exclusion, the single is called obvious.

The numbers 1, 5, 6, 9 are excluded - they are in the row.

2, 3, 8 - located in the column.

6, 7, 8 - may be present in the area.

The only candidate in cell E6 is 4.

**1.2. Hidden singles**

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

In the seventh and ninth rows, 8 was originally inscribed.

8 is in column A.

In the lower left area, 8 can only be entered in one cell - B8, so the rest of the candidates must be excluded.

**2. Exclusion of candidates**

This method allows you to reduce the number of possible candidates, so that later you can find the only correct value.

**2.1. Segment 1**

If it is possible to determine that the number can be inscribed in a single cell, it is excluded from the candidates in the row, column and area.

In the upper right area, 6 should be in segments G1 or H1 (there are no other options - the second row and third column are occupied), so the number can be excluded from the candidates for cell C1.

**2.2. Segment 2**

If a number can only be in one area, it must be excluded from candidates in other cells.

The number 2 can be written in the third row of the second area - D3 or E3. Therefore, 2 can be excluded from the candidates for the cells of the first and second rows of this area.

Taking into account the already assigned numbers of the third row, as well as columns B and H, the number 2 can only be in the second area in the third row and can be excluded from D1, E1, E2 and F2.

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