Sudoku Academy

There are 2 fundamental techniques you need to be able to use to start solving Sudoku grids, Single Position and Single Candidate.

Let's have a look at Single Candidate!

Have a look at the highlighted cell, what value can't that cell be?

There is already a 1, 5, 6, and 7 in this row.

There is already a 2, 8, 9 in this column.

There is already a 3 and 6 in the same region.

Put all of this together and we know that the highlighted cell can't be any of 1, 2, 3, 5, 6, 7, 8 or 9.
The only value (Single Candidate) left is 4, i.e. the highlighted cell must be 4.

There are 3 cells highlighted in this grid, they are solvable using the Single Candidate technique.

Can you work out the values that should be in each of the cells?

Look at each cell in turn, and methodically look for the numbers 1 -> 9 in the same row/column/region.

Did you spot these values for the highlighted cells using the Single Candidate technique?

This example is a little harder - values can inserted in the 3 highlighted cells using the Single Candidate technique.

Can you work out the values for each cell?

Did you find these values?

There are 3 cells highlighted in this grid, but only one of them is solvable using the Single Candidate technique, can you spot which one?

Look carefully at each cell, which cells have multiple values that can be inserted, and which cell has only a Single Candidate?

The highlighted cell in the top left has candidates 2, 3, 4, 6, or 9; we definitely can't insert value in this cell.

The highlighted cell in the bottom right has candidates 7 or 8. This is almost a Single Candidate cell, but not quite.

There are 3 cells in this grid that are solvable using Single Candidate, can you spot 1 of them?

The best place to start for spotting Single Candidates is to look at rows/columns/region that are already mostly filled.

Did you spot any of these Single Candidates?

That's everything you need to know about the Single Candidate technique.

You need to know the Single Position technique, and you are then ready to start tackling some of our easy Sudoku puzzles!