Sudoku techniques · Expert
Y-Wing in Sudoku
A Y-Wing is three bivalue cells arranged so that one, the pivot, sees both others, the wings. The pivot holds candidates AB, one wing AC and the other BC. Whichever way the pivot falls, one of the wings is forced to be C, so any cell that sees both wings cannot be C.
Also known as: XY-Wing.
Why it works
A pivot forces at least one of its two wings to hold their shared number, so any cell that sees both wings loses that candidate.
How to spot it
Start from a bivalue cell and treat it as a candidate pivot.
- Find two more bivalue cells the pivot can see, one sharing each of its two candidates.
- Those two wings must share a third candidate with each other. That shared number is the one you eliminate.
- The eliminations land where the wings' lines and boxes overlap, frequently a cell that touches neither the pivot nor anything you were watching.
Builds on
Worked example
These are the app's own lesson boards. Step through them the same way a hint does.
- 1
The pivot is a bivalue cell with 3 and 7, and it sees two bivalue wings: one with 3 and 5, the other with 7 and 5. This forms a Y-Wing!
- 2
Since at least one of the two wings must be 5, we can remove the candidate 5 from any other cell that sees both wings.