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Arctic Sudoku
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Hard

Y-Wing (XY-Wing)

What it is

Three cells with two candidates each – a pivot and two wings – remove a digit from cells that see both wings.

How to spot it

Find a cell with two candidates XY (the pivot). It must see one cell with XZ and another with YZ (the wings). Whatever the pivot is, one wing becomes Z.

Example

1231234567891213233438
  • Basis
  • Removed / placed
The pivot r1c1 is 1 or 2. If it's 1, the wing r1c5 is 3; if it's 2, the wing r3c2 is 3. One wing is always 3, so 3 is removed from cells that see both wings: r1c3 and r3c5.

Used from level: Hard