The New Sudoku Players' Forum

[Sue De Coq]

Here's a fascinating puzzle, taken from the Sudoku Programmers group on Google. The claim is that it's not possible to make a single move by purely logical means:

Code: Select all

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

[shakers]

The Sudoku program from here agrees, describing it as an invalid puzzle. I think I'll side with it

[Guest]

Yes. That looks fairly dull. Of course, this gets one into the whole "T&E" debate ... the clues do not work to reduce the list of possible numbers to one in any cell by applying the toolkit of normal deductive methods but this does not necessarily make the puzzle unsolvable, of course.

[Guest]

Why would this be fascinating?

It ain't that difficul to create a puzzle without any logical moves (or atleast not in the starting grid)...

For example:

1 2 3 | 4 5 6 | 7 8 9
4 5 6 | 7 8 9 | 1 2 3
7 8 9 | 1 2 3 | 4 5 6
---------------------
2 3 4 | 5 6 7 | 8 9 1
5 6 7 | 8 9 1 | 2 3 4
8 9 1 | 2 3 4 | 5 6 7
---------------------
* * * | * * * | * * *
* * * | * * * | * * *
* * * | * * * | * * *

Ofcourse such a puzzle is solvable, but it has multiple solutions.

[Norb]

Here's a fascinating puzzle, taken from the Sudoku Programmers group on Google. The claim is that it's not possible to make a single move by purely logical means:

Code: Select all

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

but did it have a unique solution?

[Guest]

Hi,

I just ran this through a program "Sudoku Solver V1.2" and I got this solution (below). Though I ahve no idea if this is the only solution - did nto have the time to check that out

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