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Problem with The Times Killer Su Doku.

 
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Glassman



Joined: 21 Oct 2005
Posts: 50
Location: England

PostPosted: Thu Feb 02, 2006 7:06 am    Post subject: Problem with The Times Killer Su Doku. Reply with quote

Hi everyone.

I received three copies of The Times Killer Su Doku book as Christmas presents!

This book is causing me difficulties. The problem is that the introduction is ambiguous. The rules state
Quote:
The joined squares must be filled with numbers that total the printed number

It then goes on to cite examples, thus
Quote:
... in the case of three joined squares, if the printed number is 6, the only combination possible is 1, 2 and 3; ...

You can see the problem. If you accept the rule then there is not one combination possible, there are two, 1, 2 and 3, and 1, 1 and 4, this last possible with an L-shaped configuration over one or two box boundaries. If you accept the example, then the rule should have been modified to read
Quote:
The joined squares must be filled with different numbers that total the printed number

So I decided, in the interests of proving uniqueness, to follow the original rule, and allow any numbers in joined squares, including duplicates. So I worked through "Gentle", "Moderate" and "Tricky", completing puzzles 173. Some of these were very tough. There were no duplicates in joined cells. Unfortunately, I had not resolved the original problem, as the compiler could have saved duplicates in joined cells for categories "Tough" and "Deadly", irritating but possible.

I am now stuck on puzzle 74. After the trivial exercise of completing the two corner cells of the centre box, with their partners, I have come to a grinding halt. If you work to the modified rule then r6c3 can only be a 6. Working to the original rule there is no such obvious starting point; the whole puzzle seems to be too loosely defined, at least I cannot find any productive strategy.

I would be grateful for help with a strategy for this particular puzzle, allowing duplicates.

Also what are your views on The Times producing a book of this type, very obviously not properly tested on a reasonable sample of established Sudoku enthusiasts. I think it is sloppy, not what you expect from the world's most famous newspaper.

Oh, and, better late than never, a happy new year to you all.

Glassman Cool
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Glassman



Joined: 21 Oct 2005
Posts: 50
Location: England

PostPosted: Tue Feb 21, 2006 1:03 am    Post subject: Reply with quote

I've now finished all the puzzles in the book. As often happens with sudoku and its variants, the most difficult classification contains the most elegant and interesting puzzles. One of these is quite beautiful, with the solution route spiralling outwards from the centre.

Apropos my original query, all the puzzles in the book follow one set of rules, apart from No. 91, by a different author.

I found it interesting developing solution strategies.

Does anyone know of a source for further puzzles of this type?

Glassman Cool
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keith



Joined: 19 Sep 2005
Posts: 3184
Location: near Detroit, Michigan, USA

PostPosted: Tue Feb 21, 2006 1:23 am    Post subject: samunamupure Reply with quote

Glassman,

Apparently the Japanese term for these puzzles is: samunamupure

Take a look at

http://www.timesonline.co.uk/article/0,,7-1757275,00.html

or this Google search result:

http://www.google.com/search?hl=en&q=samunamupure&btnG=Google+Search

Keith
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PostPosted: Tue Feb 21, 2006 9:46 am    Post subject: Reply with quote

The best site is http://www.djape.net/sudoku/wp/

The puzzles here vary in difficulty from Easy to Insane, but all are more difficult - and satisfying - than the Times ones.
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