## Only one right answer?

Everything about Sudoku that doesn't fit in one of the other sections

### Only one right answer?

I am relatively new to Suduku and am really enjoying it. I have one question though...Can someone tell me if there is only one correct answer to a puzzle. I have been working through some puzzles and I understand the rules of only one number 1-9 per column, row and 3x3 square. When I complete the puzzle I have followed those rules and I consistently find that my completed puzzle is different than the one that is supplied in the answer book. Am I missing something and doing something wrong or is it possible to have more than one way of completing a puzzle. Thank-you for your help and I look forward to a response because this is driving me crazy!
Kori
maybroda

Posts: 1
Joined: 09 August 2006

If a puzzle has more than one solution and that is not explicitley pointed out, then its a shame, because normally you cant solve it without guessing.
ravel

Posts: 998
Joined: 21 February 2006

It very much depends on whose puzzles you are doing. You don't mention the book so it's difficult to say if the puzzles have more than one answer.

Pappocom's puzzles have only one answer and they can be found in the Times Books and books by Wayne Gould. Nikoli's puzzles have only one answer and they can be found in a variety of books.

It would be more helpful if you could at least name the book you are working from.

Luna
lunababy_moonchild

Posts: 659
Joined: 23 March 2005

Sudoku - puzzles with a single unique solution.

Pseudoku - puzzles with multiple solutions.
udosuk

Posts: 2698
Joined: 17 July 2005

Why not post one (or two) of your puzzles to this forum and see how many solutions other people find. it may be that the puzzle book you are using is not a good source of puzzles.

Alternatively put some of the puzzles into some of the software available for solving them. here's a link to the software I produced:
http://uk.geocities.com/aidan_001/software.html
The brute force solver will tell you if a puzzle is not unique.
ab

Posts: 451
Joined: 06 September 2005

My wife bought me some Sudoku software at Walgreens, for about \$2.00 I think, that has zillions of bugs. There are around 700 puzzles, about 20% of which seem to have dual solutions. In these, the duality invariably forms a rectangle -- for example, there might be two ways to fill in the final four cells at r5c5, r5c9, r6c5, r6c9.

Bill Smythe
Smythe Dakota

Posts: 555
Joined: 11 February 2006

add it to the hall of shame thread Bill:
http://forum.enjoysudoku.com/viewtopic.php?t=3071
all the puzzles it produces have unique solutions. If you feel the need to reward me for my efforts, go and buy one of my sudoku t-shirts.
ab

Posts: 451
Joined: 06 September 2005

The \$2 price tag for the Walgreens software hardly merits putting it into the Hall of Shame -- what would one expect for that price?

If there's a dual solution (for the last 4 cells only), what's the big deal? It still provides hours of entertainment, for us casual solvers anyway, considering the number of puzzles provided.

A dual solution, though, could really throw a monkey wrench into anybody using uniqueness methods to solve a puzzle. Such a person might rule out a "valid" solution (if a dual solution can be regarded as valid) and eventually conclude there is NO solution.

Bill Smythe
Smythe Dakota

Posts: 555
Joined: 11 February 2006

Smythe Dakota wrote:The \$2 price tag for the Walgreens software hardly merits putting it into the Hall of Shame -- what would one expect for that price?

I disagree strongly. They are asking you for money for something of a poor quality. i am offering you a similar product for free only the quality is much higher.
ab

Posts: 451
Joined: 06 September 2005