# Stuck on this Sudoku!

I have tried every trick I can think of... where am I going wrong?

• Why wouldn't you be able to switch the one and the seven in the middle left box and then also switch the two and seven in the middle right box? – PotatoLatte Jul 27 '18 at 0:33
• @ZaniXu In the middle-right box, the 1 can only be on the second line. That's why you cannot put the 1 on the second line of the middle-left box. – xhienne Jul 27 '18 at 1:17
• – JonMark Perry Jul 27 '18 at 1:55

You have an X-cycle - both the options for 5, the green 5's and the purple 5's, eliminate the yellow 5.

• The solver doesn't actually solve any cells until it performs an "Alternate Inference Chain", though. – Riking Jul 27 '18 at 4:31

Top row, first empty cell : there are two possibilities 8 and 9

If it is an 8, there is no other 8 in the top-left region
If it is a 9, other empty cells in the same row are respectively 6 and 8. Then last two empty cells of the second row are respectively 9 and 3. Fifth cell of the second row is then an 8.
Therefore in either case, there is no 8 in the first two empty cells of the second row. First empty cell of the second row is then a 2.

You can also use the same reasoning to eliminate other possibilities. In the central cell of the middle-left region there are two possibilities : 4 and 6

If it is a 4, there is no other 4 on the same row
If it is a 6, there is a 5 in the highlighted cell (the blue one in the top-left region). Then there is a 4 in the second empty cell of the middle line.
Therefore in either case, there is no 4 in the central cell (middle region), or in the first empty cell of the sixth line.

And so on...

• Thanks everyone! I actually ended up just doing trial and error- ended up being easier in the end 🙄 – Rizza354 Jul 27 '18 at 15:33