XY-Wing
A pivot cell holding {X, Y} with two pincer cells holding {X, Z} and {Y, Z}. Any cell that sees both pincers loses Z.
Advanced sudoku technique
What it is
XY-Wing is the simplest chain technique in sudoku. It needs three cells, each with EXACTLY two candidates, arranged as: - A 'pivot' cell holding {X, Y} - A 'pincer A' cell holding {X, Z}, sharing a unit (row, column, or box) with the pivot - A 'pincer B' cell holding {Y, Z}, sharing a unit with the pivot (the unit can be different from pincer A's) Whatever the pivot ends up holding, one of the pincers is forced to Z. If the pivot is X, pincer A becomes Z. If the pivot is Y, pincer B becomes Z. Either way, ONE of the pincers will end up as Z. Therefore Z can be eliminated from every cell that sees BOTH pincers. Despite the name, no diagonal X shape is required — the technique is named after the {X, Y} pivot and the {X, Z}/{Y, Z} pincers.
Want the full theory?
The XY-Wing guide on Sudoku247Wiki walks through the logic step by step, with worked examples, diagrams and FAQs.
Read the full XY-Wing guide →Try it
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