## Sudokus of Shame

Everything about Sudoku that doesn't fit in one of the other sections
Just made a stupid mistake. The puzzle I claimed having duplicate solution was valid. Sorry for any misleading statement!
Last edited by udosuk on Mon Mar 13, 2006 8:46 pm, edited 1 time in total.
udosuk

Posts: 2698
Joined: 17 July 2005

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?
jimbob

Posts: 47
Joined: 07 March 2006

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
Moschopulus

Posts: 256
Joined: 16 July 2005

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

Posts: 186
Joined: 26 August 2005

Chessmaster

Posts: 191
Joined: 21 December 2005

Elroy wrote: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.
beetjepeetje

Posts: 9
Joined: 22 July 2006

Chessmaster wrote: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.)
robert@fm

Posts: 28
Joined: 20 February 2006

i lied in this post
Kunegochu

Posts: 47
Joined: 20 January 2008

### Re: Sudokus of Shame

Moschopulus wrote: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
Smythe Dakota

Posts: 565
Joined: 11 February 2006

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
ab

Posts: 451
Joined: 06 September 2005

ab wrote: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

m_b_metcalf
2017 Supporter

Posts: 11122
Joined: 15 May 2006
Location: Berlin

Ruud wrote: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
mizuki

Posts: 15
Joined: 03 December 2007

### Shame on Northwest Airlines

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
2017 Supporter

Posts: 216
Joined: 03 April 2006

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
keith
2017 Supporter

Posts: 216
Joined: 03 April 2006

keith wrote: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 7Common 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

m_b_metcalf
2017 Supporter

Posts: 11122
Joined: 15 May 2006
Location: Berlin

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