Simply Sudoku Blog

I’ve been working on a hard Sudoku puzzle for a few hours now, and it’s driving me crazy. I have access to the solution, but I want to understand how I can solve it.

The solution so far is as follows:

————————-
| 6 3 ? | 8 ? 5 | ? ? ? |
| ? ? 1 | 3 ? 2 | 8 6 ? |
| 8 2 ? | ? 4 6 | ? 3 ? |
————————-
| 3 6 ? | ? 8 7 | 1 ? 2 |
| ? ? 2 | ? 6 1 | 3 8 ? |
| 4 1 8 | 9 2 3 | 5 7 6 |
————————-
| ? 9 6 | ? 3 4 | ? 1 8 |
| ? 8 3 | ? ? 9 | 6 ? ? |
| ? ? ? | 6 ? 8 | ? ? 3 |
————————-

How would you make the next move and why?

5 is in column 1 row 7

I always write the ‘possible numbers for each box at the top of a box.
look at the number 5
In the middle grid 5 has to be in column 4. Therefore in the bottom middle grid it has to be in column 5.
In the top right grid the 5 has to be in column 8 row 2 or column 8 row 3 (the important part is that it has to be in column Therefore in bottom right grid the "5" has to be in column 7.

In the bottom grids the 5 has to be in rows 7 and 8 for both the middle and right grids. It can’t be in row 7 for either of these grids as that cell is already occupied. Therefore the 5 in the left grid must be in row 7. The only position is row 7 column 1.

Similarly 4 has to be in row 8 columns 1 or 2. therefore it has to be in row 7 columns 7 and 8. therefore in column 6 it cant be in rows 7 or 9 it also can’t be row 3 as there is alrady a 4 in row 3 column 5. therefore there has to be a 4 in row 1 column 6. then there has to be a 4 in row 2 column 2, a 4 in row 8 column 3.

There has to be a 1 and 2 in row 1 rows 7 and 8. Therefore there is a 7 in row 9 column 2.
I’m still working on this, but have to go out now!