Dual linking
The dual linking technique is applied when two numbers can only go in two cells of a row, column or block, and these cells do not contain other numbers.
Use when two cells in the same unit share the exact same two candidates.
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Two cells in the row are limited to the same pair, {3,8}.
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Those digits are locked between them, so 3 and 8 leave every other cell of the row.
Imagine a sudoku where in a specific row, only cells A2 and A8 can contain numbers 3 and 7. If we solve that A2 must contain 3, we automatically know that A8 must contain 7.
- Treating cells as a pair when one of them has a third candidate — both must hold exactly the same two.
- Forgetting that the elimination only applies inside the unit the pair shares.
Frequently asked questions
What is a naked pair?
Two cells in a unit limited to the same two candidates. They lock those digits between them, clearing the pair from the rest of the unit.