Pointing pairs technique

Strategy #10 for solving Sudoku: Pointing pairs technique 

Personally, I often use this strategy to solve both simple and challenging Sudoku puzzles. It's one of my favorite techniques because it's simple yet helps to quickly find solutions to the puzzle.

Here's how it works:

1. Start by filling in all the empty cells of the game board with assumptions of numbers that could theoretically be placed in those cells.
2. Look for two cells within each 3x3 block that share a common number and that number appears only in those two cells.
3. If the two found cells are in the same row or column - congratulations, move on to the next step. Otherwise, repeat the actions in step 2.
4. Imagine that the two cells horizontally or vertically form a line of fire respectively.
5. Remove the assumed number from all cells in the row except for the two found cells if they are on the same horizontal line. Remove the assumed number from all cells in the column except for the two base cells if they are on the same vertical line.

Above, on the left game board, you can see an example of applying the Pointing Pairs technique, and on the right game board is the result of executing this tactic.

Let's analyze the train of thought. On the left side of the board, in the third and fifth blocks, I found pairs that are unique to these blocks and are on the same vertical line. For the third block, it's the number 5 (highlighted in yellow), and for the fifth block, it's the number 3 (highlighted in blue). According to our strategy, numbers 5 and 3 are definitely in these cells, so horizontally they cannot appear anywhere else as it contradicts the rules of Sudoku. Therefore, we can confidently remove 3 and 5 from the specified columns respectively from our assumptions and get one step closer to solving the puzzle.

Please note that we've only looked at two cases of this technique, but in reality, there could be more on this game board. If you found this technique interesting, be sure to try playing Sudoku online on our website. Don't forget to leave comments below the article.