Sudoku techniques · Easy
Last Remaining Cell in Sudoku
The Last Remaining Cell is the simplest move in Sudoku. When a row, column or box has exactly one empty cell, that cell holds the one number missing from the unit. No candidates, no notes, no reasoning beyond counting to nine.
Also known as: Full House, Last Digit.
Why it works
If a row, column, or box has only one empty cell, its missing number must go in that cell.
How to spot it
Look for units that are nearly full rather than for cells that look promising. After every number you write, glance along its row, down its column and around its box: you have just made three units one step closer to being finished.
- Count the filled cells in a unit; eight means a free move.
- Recently completed boxes are the best place to look, because your last placement was in one.
- This is the only technique that never needs pencil marks, which is why it is the first one the app teaches.
Worked example
These are the app's own lesson boards. Step through them the same way a hint does.
- 1
There is only one empty cell left in this row.
- 2
The only possible number is 2!