Sudokus of Shame

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

Postby udosuk » Mon Mar 13, 2006 8:21 pm

[Edit]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.
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Postby jimbob » Mon Mar 13, 2006 8:54 pm

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?
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Postby Moschopulus » Sun Mar 19, 2006 10:10 pm

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
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Postby evert » Wed Mar 22, 2006 12:21 am

Heey fantastic sticky
I'm just wondering why it wasn't sticked at the bottom of this forum instead of on top:D:D
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Postby Chessmaster » Fri Apr 07, 2006 11:01 pm

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Postby beetjepeetje » Wed Aug 02, 2006 1:38 pm

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.
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Postby robert@fm » Sun Oct 29, 2006 8:43 pm

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.)
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Postby Kunegochu » Fri Feb 08, 2008 6:03 pm

i lied in this post
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Re: Sudokus of Shame

Postby Smythe Dakota » Sat Feb 09, 2008 6:20 am

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.

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Postby ab » Mon Apr 14, 2008 8:14 pm

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:(
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Postby m_b_metcalf » Mon Apr 14, 2008 8:50 pm

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
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Postby mizuki » Fri Apr 18, 2008 11:33 am

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
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Shame on Northwest Airlines

Postby keith » Thu May 01, 2008 12:12 am

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
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Postby keith » Sat May 03, 2008 2:15 pm

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
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Postby m_b_metcalf » Sat May 03, 2008 3:39 pm

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 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
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