## Not a single logical move!

Advanced methods and approaches for solving Sudoku puzzles

### Not a single logical move!

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 .`
Sue De Coq

Posts: 93
Joined: 01 April 2005

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

Posts: 93
Joined: 10 March 2005

### A barren desert

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.
Guest

Posts: 312
Joined: 25 November 2005

### Re: Not a single logical move!

Sue De Coq wrote: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?
Norb

Posts: 6
Joined: 21 May 2005

### Solution!

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
Guest