Advanced Sudoku Tips and Tricks – Swordfish Strategy

Following on from my previous post on advanced Sudoku tips and tricks, in which I introduced the X wing strategy. This post is an introduction to an even more difficult method. In fact it is one of the most complex Sudoku strategies, and that is the Swordfish technique. Please note, this is just an overview, for now of this technique. A more detailed tutorial will follow in due course, once I have outlined all the different Sudoku strategy methods.

Contents: Introduction to Swordfish | Swordfish Row Variation | Swordfish Column Variation | Swordfish Advanced Tips & Tricks

Introduction to Swordfish Sudoku
In effect, the Swordfish method is the same as X wing technique but where the X wing requires you to spot patterns over two rows and columns; the Swordfish uses three rows and columns.

As with the X wing there are 2 variations to this Swordfish strategy – the row and column variation. In order to help you spot if any of these strategies can be used, it is easier if you mark your possible candidates with pencil notations in the grid.

The Swordfish row variation
For this scenario, you are looking for three rows where there are two or three possible cells for which a particular number can be put in. And, simultaneously, for all three rows these cells must lie in the same three columns.

sudoku swordfish row variation

sudoku swordfish row variation

The Swordfish column variation
For this scenario, you are looking for three columns where there are two or three possible cells for which a particular number can be put in. And, simultaneously, for all three columns these cells must lie in the same three rows.

sudoku swordfish column variation

sudoku swordfish column variation

Swordfish Sudoku Tips & Tricks
* To use the row variation of the Swordfish method, you are looking for where you can eliminate a particular number from all the other cells in the three columns.
* And vice versa for the column variation.
* As the Swordfish strategy is a difficult one to spot, you may find it easier to focus on one number at a time. And evaluate each number against your pencil notations, for each row and then each column, in turn.
* For more advanced Sudoku strategy tips, video tutorials and examples:

Sudoku Strategy Tips

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