Description

A Hidden Pair is two cells that are part of the same group and contain the same two candidates which are not present in any other cells in the group. The two hidden pair cells should contain more than the two identical candidates. This means that we can remove all other candidates from the Hidden Pair cells other than the hidden candidates.

Reasoning

If the hidden pair candidates only appear twice in the group and only in these two cells, they must be the solutions for the cells. Therefore all other candidates in the two hidden pair cells can be elliminated.

Examples

Box Example

7 and 4 form the hidden pair in Box 6.

Row Example

5 and 6 form the hidden pair in Row 1.

Column Example

4 and 9 form the hidden pair in Column 7.

Algorithm

1. Fill in all the pencil marks in the puzzle.
2. For every box, row and column
1. Look for any 2 cells that have two candidates that only appear in 2 cells in that group.
2. Once you find a hidden pair, you can remove all the other candidates from the hidden pair cells.

Practice Puzzles

If you tap on the following links on an iOS device which has the Sudoku Tutor app installed, it will launch the app and open the practice puzzle. Tap hint once the puzzle is open to see the strategy in action.

Sample Puzzle 1
Sample Puzzle 2
Sample Puzzle 3

Next Step

Back to Sudoku Solvers or continue to next algorithm Naked Triple