Naked triple
Three cells in a unit sharing only three candidates between them. Harder to see than a pair because no single cell has to look unusual.
How to spot one
- Look for three cells in the same unit whose candidates, put together, come to exactly three digits.
- None of them has to hold all three; two candidates each is enough, as long as the union is three.
- Those three digits belong to those three cells, so no other cell in the unit can take any of them.
A real example
This grid is not a drawing. It came out of our generator, and the position below is one a solver actually reaches: every digit the reasoning uses is on the board, so you can check it yourself without taking anything on trust. The reasoning sits in column 9, shaded blue. The cells it looks at are green; the cells it changes are amber.
The same move on a different grid
One example can be a fluke of the grid it sits in, so here is another, dug at
expert from the seed second:naked-triple:153 with
26 starting digits. The technique fires in a different place, for a
different digit, and the point is what it buys you afterwards.
What the solver does next, from exactly that position:
- hidden single — In row 2, 5 has only one cell left it can go in. r2c4 takes 5, the only digit it had left.
- hidden single — In row 2, 3 has only one cell left it can go in. r2c7 takes 3, the only digit it had left.
- hidden single — In row 1, 3 has only one cell left it can go in. r1c4 takes 3, the only digit it had left.
That is the pay-off a naked triple is worth: not the one cell it names, but the run of cheap moves it unlocks behind it.
Where you meet it
Our grids are graded by the hardest technique they force, so a naked triple is what makes a expert grid what it is. Goes past the standard techniques. Take your time. When you ask for a hint on one of them, the first thing the game says is the name of the technique and which row, column or box to use it in, and that step costs nothing — you still get to find the cell yourself.
The other techniques
Ready to use it? Play expert sudoku, take on the daily grid, or start from how to play.