## 16 March 2007

### Ripped off Again

My collection of toys was augmented last month by this device:

Notice the puzzle displayed in the image:

8 4 . . . . 6 . .
. 2 . . 6 8 3 . 4
3 . . . 1 . 9 . 8
. . . . . . . . 3
2 8 5 7 9 . . . .
1 . . . 2 6 . 9 7
. . 8 . . 5 . 4 .
5 9 . 2 . . . 8 6
. 7 2 6 . 9 . 3 .

Unlike a proper sudoku, the grid does not have a unique solution. Any of the following three filled grids are possible:

Solution 1
8 4 1 9 3 7 6 5 2
7 2 9 5 6 8 3 1 4
3 5 6 4 1 2 9 7 8
9 6 7 1 5 4 8 2 3
2 8 5 7 9 3 4 6 1
1 3 4 8 2 6 5 9 7
6 1 8 3 7 5 2 4 9
5 9 3 2 4 1 7 8 6
4 7 2 6 8 9 1 3 5

Solution 2
8 4 1 9 3 7 6 5 2
9 2 7 5 6 8 3 1 4
3 5 6 4 1 2 9 7 8
7 6 9 1 5 4 8 2 3
2 8 5 7 9 3 4 6 1
1 3 4 8 2 6 5 9 7
6 1 8 3 7 5 2 4 9
5 9 3 2 4 1 7 8 6
4 7 2 6 8 9 1 3 5

Solution 3
8 4 9 5 3 7 6 1 2
7 2 1 9 6 8 3 5 4
3 5 6 4 1 2 9 7 8
9 6 7 1 5 4 8 2 3
2 8 5 7 9 3 4 6 1
1 3 4 8 2 6 5 9 7
6 1 8 3 7 5 2 4 9
5 9 3 2 4 1 7 8 6
4 7 2 6 8 9 1 3 5

My experience with the device has exposed more errors of this kind. On "Medium" difficulty, I got the following grid:

4 3 . . 1 8 . . .
5 . . . . . . . 1
. 9 1 . . . . 6 4
. . 3 . . . 7 . 6
9 . . . 6 . . . .
6 . 5 . . . . 9 .
. . . . 7 6 . . 9
. 6 . . 5 . . . 7
. . . 8 . . . . .

I will not enumerate here the 13748 solutions my trusty xemacs mode found for that grid. The only one the machine accepts as correct is number 10310.

Does anybody have Carol Vorderman's email address?

Since I installed Rockbox on my M5 there's no need to use it anyway, but it's really my public duty to complain.