Sudoku Cross Hatching

 Today we’re going to talk about a very quick and convenient method to solve an easy Sudoku puzzle. This article will be especially interesting for beginners and people who have never played Sudoku before.

Cross hatching is an algorithm that helps solve Sudoku effortlessly. The core idea of this strategy is to identify cells on the Sudoku grid that can contain the current digit in only one place within a 3x3 block.

Let’s move on to the actual strategy and go through a real example of solving a Sudoku puzzle using this method.

Step 1 Choose the starting digit you will work with. I always begin with the number 1. You can start with any other digit.

Step 2 Take note of the positions where the current digit is already placed on the Sudoku grid.

Step 3 According to Sudoku rules, each placed digit “fires” across its row and column. This means the current digit cannot be placed in any of the affected cells along that row or column.

Step 4 Repeat Step 3 for every cell that contains the current digit.

Step 5 After this “firing,” the dead cells are those where the current digit cannot go. Focus on the surviving cells. If there is only one surviving cell left in a 3x3 block, you can confidently place the current digit in it.

Step 6 If there are 2 or 3 surviving cells in a block, and they are aligned either horizontally or vertically, that means the current digit can only be in those cells within that block. As a result, the current digit cannot be in any of the same-line cells in the other blocks — those cells are also “fired upon” accordingly, depending on their alignment.

Step 7 Once all the “shots” for the current digit have been made and all clearly empty cells are filled with the correct digits, you can confidently move on to the next digit and restart the algorithm from Step 1.

This is a rather simple and highly effective method of solving Sudoku. There are puzzles that can be solved from start to finish using only the cross hatching (laser strike) method. 

If you have any questions or feedback, feel free to leave a comment below this article. Enjoy solving Sudoku!