Below the Sudoku board you will find discussions about the techniques used to solve this Sudoku. Use the buttons to the right and left of the board to step through.
Techniques used in this Sudoku:
This is the strategy we will use:
Box Row Column and Triangulation:
Box Row Column and Triangulation:
Box Row Column:
Box Row Column:
Box Row Column and Triangulation:
Box Row Column:
Box Row Column and Triangulation:
Box Row Column:
Box Row Column and Triangulation:
Box Row Column:
Box Row Column:
Box Row Column:
Last Free Cell:
Box Row Column:
We are out of options. Time to use Notes.
To create notes, we search for all possible solutions for each free cell. Notes are very tedious and error-prone. So instead of writing notes in all the free cells, we wrote notes for boxes 1 and 2, which have only 2 free cells each. There are two possible solutions for each cell, so these notes won't help much.
We have added notes in boxes 5 and 8. We now have two cells (E4, H1) with only one possibility (Obvious Singles). But before we write these numbers, we should check that there are no other possible numbers in these cells. You shouldn't trust your notes blindly, because it's very easy to make mistakes when writing them.
Obvious Singles
1 in E4 and H5. New cells available!
Obvious Singles
7 in A5 and 4 in I6. New cells available!
Obvious Singles
1 in A6 and 4 in E4. No more cells with a single value. Time to add notes in boxes 7, and 9.
Obvious Singles
Only one cell (E8).
Obvious Singles
Write the number and we now have more cells available.
Obvious Singles
Write the numbers and 7 new cells appear!
Write the numbers...
new cells...
Write the numbers...
and we're done!