Hidden Singles
Hidden Singles are the backbone of sudoku solving. When a number can only go in one place in a row, column, or box, that's where it belongs.
Beginner
What are Hidden Singles?
A Hidden Single is a cell where a particular number is the only candidate that fits in that row, column, or box. Although the cell itself may have multiple candidates, there's only one place where that specific number can go.
How to Find Hidden Singles
- Choose a number from 1-9 to analyze
- Scan each row, column, and box to see where this number can go
- If the number can only go in one place in a group, fill it in there
Example
In box 5, the candidates for a cell might be {1,4,7}, but when you look at the whole box, this is the only cell where a 7 can go. Then the answer is 7, even though there are other candidates.
Pro Tips
- Start every puzzle by looking for Hidden Singles
- Scan systematically: first all rows, then columns, then boxes