X-Wing Strategy in Sudoku: Master This Advanced Solving Technique

1. Understanding X-Wing Basics

Whether you are playing sudoku online or with a paper version you’ll want to know how to narrow down possibilities on the board. The good news is that there is a strategy that can help you do that and it's the X-Wing.

What is the X-Wing move?

While it sounds like something out of Star Wars, the X-Wing is a clever sudoku move. It does form an X through and that is where it gets its name as well see below. The X-Wing sudoku strategy is useful because it focuses on a single number, helping you to limit the cells in which that number could appear. In this way, it can help speed up your game.

2. Identifying X-Wing Patterns

Before you can complete the X-Wing strategy you will need to be able to identify the pattern that indicates it's there in your puzzle. The good news is that although the X-Wing is an advanced technique it's pretty easy to spot.

To spot an X-Wing in sudoku you need to ignore the 3x3 blocks. Instead, your attention needs to be focused on columns or rows. You need to look for 2 rows or columns that are parallel, and that show only two potential cells for a single digit. Once you have identified these cells check to see if they form the corners of a rectangle. If they do then you have an X-Wing. Indeed, if you draw a line from the top cell in one column to the bottom cell in the other and vice versa you will create an X pattern.

Once you have your X pattern you can rest safe in the knowledge, because of the way that sudoku words that the digit only has two possibilities. Either it's in the top cell of one and the bottom of the other or vice versa, making that part of the puzzle very easy and quick to solve.

3. Applying the Technique

To apply the X-Wing sudoku technique you will need to locate either two columns or two rows on the grid where there is the possibility of a single number to occupy those cells. The cells must be positioned so they make a rectangle (or square) once connected.

Also when applying the X-Wing technique you will need to test out each set of possibilities for the number in the cell. For example, you will need to see if the upper right-hand and lower left-hand possibilities work or if the lower right-hand and the upper left-hand possibilities are correct.

4. Common Mistakes to Avoid

Watch out for false or incomplete X-Wings. This is where you find 3 sides of the square, but one is missing. Usually,y this is because the digit in question is a possibility for additional cells in the column or row. That means you can't solve it with the X-Wing tactic and have to use another instead.

5. Combining with Other Strategies

X-Wing thinking can often be used in, or combined with other types of sudoku tactics.

Swordfish Strategy

The first of these you should consider is the swordfish strategy. The swordfish strategy is very like the X-Wing, except its expanded version includes 9 cells rather than just four.

To find a swordfish on your paper or online sudoku grid you need to look for a 3x3 cell pattern where the potential number (candidate) is found on three different columns or rows. The critical benefit of the swordfish technique is that it helps players remove a number from the columns or rows if it is not part of the swordfish pattern.

A word of warning though, the swordfish technique is even more tricky than the X-Wing, so it's best to only use it if you are an advanced player.

Sudoku XY Wing

The XY Wing, also called the Y-Wing is a sudoku tactic that can be very helpful when you are in a bind. All you need to do is identify three cells that could hold one of two numbers.

To do this just find one cell on the grid that could be 1 of two digits. Then look for two more like it. Although those other two must be found in either the same block, row or column as the cell you first find. Additionally, at least one of the numbers of each of the two additional cells needs to be the same as one of the numbers in the original cell you picked. Otherwise, the math does not match!

Once you have fulfilled this criteria take a look at the cell where the other two intersect (usually in an L or reverse L pattern. You want the cell that is at the corner of the L. Once you have that, compare the candidates to the other two cells. If one of the candidates is shared by both the other cells, it can then be removed.

6. Practice Examples

In the following videos, you can see how some of the pros use X-Wings to solve their sudoku.

7. Tips for Effective Use

The most important tip for effectively using the X-Wing strategy in sudoku is to always look for a rectangle of potential candidates. If you can find the rectangle you have an X-Wing and you can use the strategy effectively to faster solve your problem.

The trick to understanding X-Wings is to imagine what would happen if you choose just one of those positions - what would it do to the others? Imagine making the top left of those cells be the 6 - it would force the other candidate out on its row, and also force the candidate in the bottom left out too (the red arrows).

8. Enhancing Your Solving Speed

The X-Wing is a strategy that if applied properly can help you solve your paper and online sudoku faster. This is because it helps to decrease the number of possibilities (candidates) in a certain row or column in the grid.

You certainly don't need to know how to do an X-Wing strategy to solve sudoku puzzles of medium difficulty upwards. But it can really help and make the entire experience faster as well.

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