Learn how Naked Pairs, Hidden Pairs, and Triples work in Sudoku with visual diagrams to lock candidate numbers and clear difficult boards.
In intermediate and advanced Sudoku, Pairs and Triples (known in Japanese as Doumei or "Allies") allow you to lock two or three candidate digits into specific cells within a row, column, or 3×3 box.
When two cells in the same row, column, or 3×3 box contain the exact same two candidates (e.g., [1, 2]), those two digits must occupy those two cells (one will be 1 and the other will be 2). Therefore, 1 and 2 can be eliminated from all other cells in that unit!
| [1, 2] | 8 | [1, 2] | 1,2, 5 | 9 | 2, 4, 6 | 3 | 7 | 1, 4, 6 |
▲ Removing 1 and 2 from the 4th cell ([1,2,5]) immediately solves it as a Naked Single 5!
When two specific candidate digits (e.g., 5 and 8) appear ONLY in the exact same two cells within a row, column, or box—even if those two cells currently hold other notes like [1, 5, 8] and [3, 5, 8, 9]—those two cells MUST become 5 and 8. You can immediately erase all other candidates (1, 3, 9) from inside those two cells!
