My Sudoku

Extreme Used in extreme puzzles.

W-Wing

Two matching pairs, one link

Take two cells with the same two candidates, X and Y, that do not see each other.

Then find a unit where Y has exactly two places, one seeing the first cell and the other seeing the second. One of those places holds Y, so the cell it sees is not Y: the two cells cannot both be Y.

So one of them is X, and a cell that sees both cannot be X: remove it there.

What to look for

Find two cells with the same two candidates, then a unit where one of those digits has two places, each seeing one of the cells.

Example

162347859498625251735738912469467516832783867426726591215978367684621735943858735413568568936283592356467157 112233445566778899
W-Wing: R7C5 and R8C2 both hold {3,5}; in row 9, 3 can only go in R9C5, which sees R7C5, or R9C2, which sees R8C2. R7C5 and R8C2 cannot both be 3, so one of them is 5: remove 5 from R8C5, R8C6.
  • The cells the technique relies on
  • Cells where it removes candidates, struck out in red
  • Strong link (solid line) and weak link (dashed)

Practise it

In the app, Learn › W-Wing sets exercises on real positions, then a full puzzle that needs this technique and nothing harder.

Practise in your browser