Variant Sudoku

W-Wing

Two cells hold the same two digits, and a house has just two spots for one of those digits, one seen by each cell. Then one of the two cells is the other digit.

Practice now
4
59
8
8
5
279
6
1
3
49
8
5
1
6
7
9
2
7
8
8
6
7
8
9
4
7
8
8
5
7
1
4
3
9
2
6
2
59
8
7
1345
Clear 5 from cells that see both.

Why it works

On the board above:

r1c8 and r9c4 can each only be 9 or 5.

Row 2 has only two spots for 9: r2c8 and r2c4. r2c8 sees r1c8, and r2c4 sees r9c4.

If neither r1c8 nor r9c4 were 5, both would be 9. Then neither r2c8 nor r2c4 could be 9, and row 2 would have no 9.

So r1c8 or r9c4 is 5. r9c8 sees both, so it can’t be 5.

How to spot it

  1. Find two matching two-candidate cells

    Same two digits, and the two cells don’t see each other.

  2. Pick one of their digits

    Call it the link digit.

  3. Find a house with two spots for it

    One spot must see the first cell, the other must see the second.

  4. Clear the other digit

    Remove it from any cell that sees both matching cells.

Practice

Real boards from the solver, with every pencil mark filled in. Spot it, then use it, then find it cold.

Loading the boards…

Try it in a real puzzle

Each of these needs a W-Wing to finish. It opens in the player.

Tips

Try both digits

Each digit of the pair can be the link. Check both before you give up.

The link can be any house

Row, column or box. It just needs exactly two spots.

SwordfishThe X-Wing with three rows: three rows whose spots use only three columns fill those columns.Next: Swordfish →

In the glossary

W-wing