The Y-Wing technique is an advanced Sudoku solving strategy that helps you eliminate candidates in certain complex scenarios. It involves identifying a specific pattern of three cells that allows you to deduce the value of one of those cells.
How to Identify a Y-Wing
A Y-Wing pattern consists of three cells with the following characteristics:
Cell A (the 'hinge'): This cell has two candidate numbers: X and Y.
Cell B (one of the 'wings'): This cell sees Cell A and has two candidate numbers: X and Z.
Cell C (the other 'wing'): This cell sees Cell A and has two candidate numbers: Y and Z.
Crucially, Cell B and Cell C must see each other.
How the Y-Wing Technique Works
If the above conditions are met, you can deduce the following:
If Cell B is not X, then Cell A must be X.
If Cell C is not Y, then Cell A must be Y.
Therefore, if Cell B is not X and Cell C is not Y, then Cell A cannot be either X or Y.
This means that any cell seen by both Cell B and Cell C cannot contain the candidate Z, as Z would force either Cell B to not be X or Cell C to not be Y.
Example of the Y-Wing Technique
Tips for Spotting Y-Wings
Look for cells with only two candidates.
Focus on cells that see each other.
Remember that the wing cells must see the hinge cell.
