The New Sudoku Players' Forum

[udosuk]

[Edit]Just made a stupid mistake. The puzzle I claimed having duplicate solution was valid. Sorry for any misleading statement!

[jimbob]

Well I didn't find 2 solutions when I did it last week. I've thrown away my solution now. I guess you've put it through DJ's Perfect Sudoku to verify there are multiple solutions.

I did the version in the paper. Did you get it from the paper or online? Could they be different?

[Moschopulus]

Another website with multiple solution puzzles is http://www.psycho-sudoku.com/1.html

as reported here
http://forum.enjoysudoku.com/viewtopic.php?t=3565&start=9

[evert]

Heey fantastic sticky
I'm just wondering why it wasn't sticked at the bottom of this forum instead of on top

[Chessmaster]

www.sudokugrandmaster.com

[beetjepeetje]

Where DOES one find valid (free) ones online, anyone know?

www.sudokunet.nl for example. It's in Dutch, but the sodukus I tried have one solution.

And you can generate sudokus with free sudoku programs, a good one is the Sudoku explainer at:
http://diuf.unifr.ch/people/juillera/Sudoku/Sudoku.html
This one is also very good to learn how to solve sudokus.

[robert@fm]

people just have to learn that ture sudokuist like their puzzles to have one solution.

Not just Sudoku -- according to an excellent Dutch book on recreational mathematics I once read (in an English translation, of course), a true puzzle always has exactly one solution.  (What annoys me are the so-called "puzzles" sometimes cited by the ignorant, that have no solution (e.g. the "Three Utilities Puzzle") -- such are problems, not puzzles.)

[Kunegochu]

i lied in this post

[Smythe Dakota]

Several posts have reported products with sudoku puzzles having more than one solution. I propose we maintain a list of these. ....

Here's another one (which I've mentioned before in other threads): Sudoku Master by Centron. It runs on a PC. My wife got it for me for about $2 at Walgreen's. (Don't know if it's still being sold.)

About 20% of the 700 included puzzles have dual solutions, invariably of the unresolvable-rectangle type. By this I mean, for example, two ways to place two 5's and two 7's in four cells such as r46c38.

The dual solutions seem to occur mostly (if not entirely) in the puzzles at the higher levels of difficulty.

Bill Smythe

[ab]

the Metro newspaper in the uk has just changed its sudoku supplier. the typeface and presentation suggests their using the same supplier as the London Paper, which provides a quality difficult puzzle each day. however something's gone wrong somewhere because this was the Metro 'challenging' puzzle:

Code: Select all

 2 . . | . . . | 7 . 5
 . . 1 | 2 . . | . . .
 . . . | . 3 . | 1 4 .
 ------+-------+------
 6 7 . | . 4 . | . . .
 8 . . | 9 . . | . . 1
 . . . | . 8 . | . 9 4
 ------+-------+------
 . 6 3 | . 9 . | . . .
 . . . | . . 6 | . . .
 1 . 5 | . 7 . | . . 6



It has multiple solutions

[m_b_metcalf]

the Metro newspaper in the uk has just changed its sudoku supplier. the typeface and presentation suggests their using the same supplier as the London Paper, which provides a quality difficult puzzle each day. however something's gone wrong somewhere because this was the Metro 'challenging' puzzle:

Code: Select all

 2 . . | . . . | 7 . 5
 . . 1 | 2 . . | . . .
 . . . | . 3 . | 1 4 .
 ------+-------+------
 6 7 . | . 4 . | . . .
 8 . . | 9 . . | . . 1
 . . . | . 8 . | . 9 4
 ------+-------+------
 . 6 3 | . 9 . | . . .
 . . . | . . 6 | . . .
 1 . 5 | . 7 . | . . 6



It has multiple solutions

Yes, 15. We see that r1c5 (which is redundant), r5c6, and r8c7 need to be present on symmetery grounds. This version has one solution but is really very hard.

Code: Select all

 2 . . . 1 . 7 . 5
 . . 1 2 . . . . .
 . . . . 3 . 1 4 .
 6 7 . . 4 . . . .
 8 . . 9 . 3 . . 1
 . . . . 8 . . 9 4
 . 6 3 . 9 . . . .
 . . . . . 6 4 . .
 1 . 5 . 7 . . . 6   SE 7.3

Regards,

Mike Metcalf

[mizuki]

I found a lot of sites that use www.free-sudokus.com as a source for their sudokus. This site is flooding the web with multiple-solution sudokus.

Only Sudokus with single solution: http://mypuzzle.org/sudoku/play.html

[keith]

With so many quality sources for puzzles available, I was surprised to find this one in the onboard magazine of NorthWest Airlines, NWA World Traveler, April 2008.

Code: Select all

Puzzle: NWAir042008
+-------+-------+-------+
| . 5 . | . . . | . 9 . |
| . 6 1 | . 9 . | 3 4 2 |
| 4 7 . | 2 . . | . . . |
+-------+-------+-------+
| 5 8 . | . . . | 1 . . |
| . 9 . | . . 4 | . 6 . |
| . 1 6 | . . . | . 5 . |
+-------+-------+-------+
| . . . | . 7 2 | . . 5 |
| 9 . . | . . . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+

Credit: Puzzle by Peter Ritmeester. PZZL.com

(Ruud: Damaging to the reputation of the Netherlands Sudoku experts?)

Anyway, it is the last day of the month. When I fly home on Friday, maybe I will find another "Sudoku of Shame" in the May issue.

Keith

[keith]

Sure enough! In the May issue of NWA World Traveler, this gem:

Code: Select all

Puzzle: NWAir052008
+-------+-------+-------+
| . 2 . | . . . | 1 . . |
| 1 4 9 | 7 . . | . . . |
| . . . | . . . | . . 3 |
+-------+-------+-------+
| . . . | . . . | . 1 6 |
| 8 . . | . 1 4 | . 5 . |
| . . 6 | . 3 8 | 7 . . |
+-------+-------+-------+
| 6 3 4 | . 7 . | . . 8 |
| . . . | . . . | 4 . . |
| . 8 . | . . . | . . . |
+-------+-------+-------+

These puzzles are not even close to being valid! You run out of steam after only a few deductions.

Note also the complete lack of symmetry.

Keith

[m_b_metcalf]

These puzzles are not even close to being valid! You run out of steam after only a few deductions.

Code: Select all

brute found 338 solutions. Last was:
 3 2 7 8 9 5 1 6 4
 1 4 9 7 6 3 2 8 5
 5 6 8 2 4 1 9 7 3
 4 5 3 9 2 7 8 1 6
 8 7 2 6 1 4 3 5 9
 9 1 6 5 3 8 7 4 2
 6 3 4 1 7 2 5 9 8
 7 9 5 3 8 6 4 2 1
 2 8 1 4 5 9 6 3 7

Common clues (34):
 3 2 . . . . 1 . .
 1 4 9 7 . 3 . . .
 . 6 . . . . . . 3
 4 . 3 . . 7 8 1 6
 8 . . 6 1 4 3 5 .
 . 1 6 . 3 8 7 . .
 6 3 4 . 7 . . . 8
 . . . . . . 4 . .
 . 8 . . . . . . .


Regards,

Mike Metcalf