XY-Wing is another advanced Sudoku technique that relies on identifying a pattern among three cells, each containing two candidates, forming an 'L' shape. It allows elimination of candidates that intersect the logic of the pivot and wings.

When to Use the XY-Wing Technique?

Use XY-Wing when you find three cells where one cell (pivot) shares one candidate with each of the other two cells (wings), and the wings share a different candidate between them. This structure allows eliminating candidates from peer cells that see both wings.

How to Identify an XY-Wing?

1. Find three cells with exactly two candidates each.
2. Confirm one cell shares a candidate with the other two (pivot and wings).
3. Ensure the wings share a candidate different from the pivot.

Practical Example

If cell A (pivot) has candidates 1 and 2, cell B (wing) has candidates 1 and 3, and cell C (wing) has candidates 2 and 3, you can eliminate candidate 3 from any cells intersecting with both wings.

Benefits of Using XY-Wing

• Eliminates impossible candidates to simplify solving.
• Effective for unlocking tricky puzzle configurations.
• Enhances pattern recognition and strategic problem solving.

Tips for Practicing XY-Wing

• Get comfortable identifying two-candidate cells and their relationships.
• Start with easier puzzles to spot XY-Wing patterns.
• Use in combination with other advanced techniques for best results.

Conclusion

Mastering the XY-Wing technique empowers Sudoku enthusiasts to solve more complex sudoku puzzles and improve overall solving efficiency.