SudokuWhat is a naked single?
A naked single is an empty cell that has only one possible candidate. Look at its row, its column, and its 3×3 box together: if eight different digits already appear there, the ninth digit is the only one left, so it must go in that cell.
How to find naked singles
- Pick a crowded area. Cells at the crossing of a full row and a full column are the best candidates.
- List the digits you can see. Go through the row, then the column, then the box, and note every digit already placed.
- Find the missing one. If exactly one digit from 1 to 9 is missing from your list, write it in.
A quick trick: count from 1 to 9 while scanning. The first digit you cannot find is a candidate; if you only find one, you have a naked single.
When to use it
Naked singles are enough to solve most Easy puzzles on their own, together with hidden singles. On harder puzzles, they keep appearing after every elimination, so always come back to them before reaching for an advanced technique.
Practice naked singlesTry the technique on a fresh Easy puzzle.
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