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Question about "givens"

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5119
Location: Rochester, NY, USA

PostPosted: Mon Jan 21, 2008 4:38 pm    Post subject: Question about "givens" Reply with quote

This is #5-209295 from Vanhegan, not that it matters, as this is representative of numerous puzzles I've seen. Note box 5, with the eight givens. Why not finish the job and give us the ninth? Is there any logical reason for the one omission?

Code:

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

Play this puzzle online at the Daily Sudoku site
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Tue Jan 22, 2008 12:51 am    Post subject: Reply with quote

I find that puzzles often have one or two really obvious "givens" at the start that can be written in immediately. I don't know how the computer programs set puzzles (nor do I wish to know) but I guess that it is something along the lines of starting with a full grid then progressively taking numbers out on a random (though usually symmetrical) pattern, and then back solving it at each step. The level of solving techniques that the computer uses determines the puzzle's rating. Eventually enough numbers would be extracted to make the puzzle "too hard". Thus the same grid yields all levels of puzzle, to be stored away for use at some later time.

This would lead to the apparent absurdity of the obvious givens - computer programs don't cast a "logical eye" over their output.

(I have had engineering students who also lack this ability!)

Cheers
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Tue Jan 22, 2008 4:19 am    Post subject: Reply with quote

I agree 100 percent with kragzy and I also agree with Marty's question becuase if you were going to make a sudoku puzzle, why not make it just a little less obvious about where to start filling in numbers.

I think the real question here isn't about the program that generated the puzzle because as kragzy said, it has no judgemental eye over how obsurd the puzzle might look. instead, it's the person who publishes it and overlooks the obsurdity.

in all fairness, a sudoku puzzle can have 80 givens. obsurd as it may sound.
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