XY-Wing
A two-candidate pivot links two pincer cells that share a third digit, which can then be eliminated from any cell both pincers see.
When to use it
Use when a two-candidate pivot sees two pincers, each sharing one of its digits plus a common third digit.
Worked example
-
A pivot {1,2} sees a pincer {1,3} and a pincer {2,3}; the two pincers share the digit 3.
-
Whatever the pivot turns out to be, one pincer becomes 3, so 3 is removed from any cell both pincers see.
Common mistakes
- Picking pincers the pivot cannot see (not sharing a row, column or box).
- Eliminating from a cell seen by only one pincer instead of both.
Frequently asked questions
What is the difference between XY-Wing and XYZ-Wing?
In an XY-Wing the pivot has two candidates and is not part of the elimination; an XYZ-Wing pivot has three, so the eliminated cell must also see the pivot.