Sudokus of Shame

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

Postby keith » Sat May 03, 2008 7:24 pm

The smoking gun:

http://msp.imirus.com/Mpowered/imirusApp.jsp?volume=nwa08&issue=5&page=120

Mike, thank you for the count of solutions. NWA used to be in bed with KLM, which is probably how they landed up with this puzzle source.

I have said in the past that I have no use for, and never look at, "yesterday's solution" for a Sudoku puzzle. But, I will ask for the solution to this one!

(If the puzzle really only has one solution, that solution is not interesting. The logical moves to get to the solution are very interesting!

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Postby tarek » Sat May 03, 2008 7:44 pm


but keith,

If the puzzle is a windoku then it has a unique solution

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Postby ronk » Sat May 03, 2008 7:45 pm

So the constraints for this puzzle are 9 rows, 9 columns and 13 boxes. Right?

There could then certainly be fewer clues than normal.
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Postby tarek » Sat May 03, 2008 7:52 pm

ronk wrote:So the constraints for this puzzle are 9 rows, 9 columns and 13 boxes. Right?

There could then certainly be fewer clues than normal.


The 4 extra boxes allow for additional 5 hidden constraints See: Sudopedia article.

The minimum until now is 11 clues.

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Postby ronk » Sat May 03, 2008 8:21 pm

tarek wrote:The 4 extra boxes allow for additional 5 hidden constraints See: Sudopedia article.

But these five "hidden constraints" are not independent of the other four, so I don't think they're necessary. Useful like the law-of-leftovers, I'm sure, but not necessary.
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Postby keith » Sun May 04, 2008 2:32 am

I noted that there were an additional four shaded 3x3 boxes, but the puzzle explanation (see posted link) does not indicate it is anything other than a normal Sudoku puzzle.

I have sent a message to the puzzle originator and to NW Airlines, we will see what they say.

Keith

[edit] But now I see in the Wikipedia article,

http://www.sudopedia.org/wiki/Hypersudoku

that
This format was first introduced in the Dutch newspaper NRC Handelsblad by Peter Ritmeester and the first playable online version by Chris McCusker.
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Postby tarek » Sun May 04, 2008 6:13 am

ronk"][quote="tarek wrote:But these five "hidden constraints" are not independent of the other four, so I don't think they're necessary. Useful like the law-of-leftovers, I'm sure, but not necessary.
Indeed, they are not needed to establish a solution through backtracking and therefore not needed to establish uniqueness. They might come in handy for a manual solver though.

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Postby udosuk » Sun May 04, 2008 12:58 pm

ronk wrote:
tarek wrote:The 4 extra boxes allow for additional 5 hidden constraints See: Sudopedia article.

But these five "hidden constraints" are not independent of the other four, so I don't think they're necessary. Useful like the law-of-leftovers, I'm sure, but not necessary.

Thinking about it, in normal sudoku, you only need 4 boxes (b1379), and the other 5 boxes are all unnecessary too. And after you establish 9 rows, you only need 8 columns as the last column must be forced to have {1..9}. So for these Windoku/Hypersudoku/NRC puzzles there are only 9 rows, 8 columns and 8 boxes.:idea:

If you're interested in these Windoku puzzles, here is one which combines Windoku, X (diagonals) and Killer (cages) but no numeric clues at all:

http://forum.enjoysudoku.com/viewtopic.php?t=6061

:)

PS: Keith, I wonder who is more at fault here, the magazine for not giving explicit written instructions about the extra boxes or you for failing to notice the 4 shaded squares might actually mean something in the puzzle? If a Sudoku novice comes across a 9x9 square with the 3x3 boxes in bolded borders but no written instructions would he instinctively know that these 3x3 boxes must not have numbers repeated like the rows/columns? If he comes across a grid with diagonals drawn out forming a big "X" would he instinctively know that numbers cannot repeat on the diagonals?:D
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Postby daj95376 » Sun May 04, 2008 1:23 pm

udosuk wrote:PS: Keith, I wonder who is more at fault here, the magazine for not giving explicit written instructions ...

You might want to review the image for the puzzle. It says to:

... every 3-by-3 box ...

This means all of the grey shaded boxes as well. However, I would have missed it as well.
Last edited by daj95376 on Sun May 04, 2008 9:37 am, edited 2 times in total.
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Postby udosuk » Sun May 04, 2008 1:31 pm

daj95376 wrote:
udosuk wrote:PS: Keith, I wonder who is more at fault here, the magazine for not giving explicit written instructions ...

You might want to review the image for the puzzle. It says to:

... every 3-by-3 box ...

This means all of the grey shaded boxes as well. However, I would have missed it as well.

For some reasons I can't access that link.:(

But even if there is this phrase "every 3-by-3 box" it still doesn't qualify as "explicit written instructions". Should have said "every 3-by-3 box (in bolded borders or shaded grey)".:D

Anyway, my point is in the logical puzzle world graphical hints are much more important than word hints. When trying Nikoli puzzles we often have to access pages of Japanese instructions. Sometimes we can use online translators such as babelfish but often we have to guess the rules from the pics. And it's all part of the fun and challenge!:D
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Postby Glyn » Sun May 04, 2008 3:34 pm

Couldn't access the page, but the grid was a trivial NRC-Windoku all singles.

Incidentally, talking of extra windows, the 4 of the NRC give 9 more groups: Could another set off 4 windows be added, shifted in diagonally from the NRC pattern reducing the givens further, or would they be redundant?
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Postby keith » Sun May 04, 2008 4:53 pm

I suppose this closes the case: From the author of the puzzle to the Editor of the magazine:

Dear editor,

This is the author of your sudoku. The introduction is missing one
vital addition: the four grey areas also need to contain numbers 1-9.
Could you please add it?

Thank you,

Peter Ritmeester
PZZL.com


I am not sure that I am at fault for not figuring out the meaning of the shaded boxes.

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Postby udosuk » Sun May 04, 2008 9:03 pm

Glyn wrote:Incidentally, talking of extra windows, the 4 of the NRC give 9 more groups: Could another set off 4 windows be added, shifted in diagonally from the NRC pattern reducing the givens further, or would they be redundant?

The extra 4 windows you proposed would be overlapping each other:
r345c345, r345c567, r567c345, r567c567

I don't see these 4 overlapping windows producing any hidden groups, but they're certainly not redundant. An example solution grid would be like this:
Code: Select all
+---+---+---+
|453|176|982|
|278|945|361|
|961|238|745|
+---+---+---+
|834|562|197|
|127|894|536|
|596|317|824|
+---+---+---+
|785|423|619|
|612|789|453|
|349|651|278|
+---+---+---+

Don't know if this variant can reduce the givens further, but without ordering the symbols (e.g. non-consecutiveness) the best you can do is a puzzle with 8 givens. With ordering/arithmetic context I have created puzzles with one shaded cell only and no numeric given whatsoever.:)

Keith wrote:I am not sure that I am at fault for not figuring out the meaning of the shaded boxes.

Opinion accepted. Certainly some people are more imaginative than others and it's definitely not a "fault" for being not imaginative enough. The magazine should have cater for the broad range of flight passengers who might not all have the imaginativity to figure out the meaning of those shaded boxes. Case closed.:idea:
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Postby keith » Sun May 04, 2008 10:11 pm

Opinion accepted. Certainly some people are more imaginative than others and it's definitely not a "fault" for being not imaginative enough. The magazine should have cater for the broad range of flight passengers who might not all have the imaginativity to figure out the meaning of those shaded boxes. Case closed. Idea

I think it goes a little further than that. The magazine should also cater to the language skills of their audience, even if they now change the (English language) puzzle instructions.

The reason I got involved with this puzzle was that my neighbor on the flight, a French Canadian with virtually no English for complicated communication, was having difficulty with it.

My own opinion is that the magazine should publish a reasonably difficult conventional Sudoku.

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Postby udosuk » Mon May 05, 2008 3:11 am

keith wrote:I think it goes a little further than that. The magazine should also cater to the language skills of their audience, even if they now change the (English language) puzzle instructions.

The reason I got involved with this puzzle was that my neighbor on the flight, a French Canadian with virtually no English for complicated communication, was having difficulty with it.

If there is a language barrier shouldn't the picture be more prominent? I can't read the magazine from your link so don't know if they have both English/French instructions but like I said above in the world of puzzles information from words might not be as important as information from pics (unless you're doing a language puzzle such as crosswords).
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