Sudoku - How to Do XY-Wings

An xy-wing can help you solve difficult puzzles.

An xy-wing is an advanced technique for solving very difficult Sudoku puzzles. The xy-wing technique allows you to eliminate options in cells and can help to break up a very difficult puzzle. It involves finding three squares with a specific pattern of numbers and eliminating choices based on these numbers.

Instructions

1. Look for a group of three cells that contain only three different numbers. The numbers in the group of cells should be in a pattern of xy, yz and xz where x, y and z can be any three numbers. The cell that contains xy is the stem cell and the other two are the branch cells.

2. Look for cells that interact with both the yz and xz cells. This may be one cell or it may be more than one cell.

3. Eliminate the z option in cells that interact with both the yz and xz cells.

4. Continue solving the puzzle using other techniques such as naked doubles and locked candidates.

Tips & Warnings

• Only look for xy wings when you have used all of the other solving techniques that you know.

• Only eliminate z in cells that interact with both the yz and xz cells. Eliminating too many options could make your puzzle unsolvable.

References

• Sudoku Essentials: Sudoku XY-Wing Solves Difficult Sudkoku Puzzles
• Sudoku Online: Sudoku Solving Techniques - XY Wing

Resources

• Sudkoku9981: Solving Sudoku Strategy - Wings
• Sudoku9x9: Sudoku Solving Techniques