The starting grid for this puzzle is:

- Code: Select all
` *-----------*`

|.8.|.2.|1.7|

|...|..5|4..|

|...|...|...|

|---+---+---|

|...|.1.|..9|

|..8|...|...|

|...|...|..5|

|---+---+---|

|4.3|..9|...|

|...|.7.|6..|

|.6.|..8|.5.|

*-----------*

Computer solvers will say it has "too many solutions to count" unless they can take account of the diagonal requirement.

Nonetheless, it is a difficult puzzle and I'm stuck! Stevens you will find it easier to start again. Consider the diagonals like any other row or column to make eliminations i.e. neither 3 nor 7 can go in any cell on the top right to bottom left diagonal and 5 cannot go in any cell on the top left to bottom right.

Also when you get to a point with only two candidate entries for a particular number on the diagonals - you can use this to eliminate at the intersecting cell. For example in this puzzle, you get to a point where 8 must be in either r4c4 or r7c7 - thus you can eliminate 8 at r4c7 and r7c4 (unless these cells are already filled).

See how you get on. I'll post where I got to later.

BTW What's the prize?