A Diagonal 17

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A Diagonal 17

Postby Moschopulus » Sun Nov 06, 2005 10:26 am

Is there a puzzle with 17 clues where all the clues are on the two diagonals?

Code: Select all
x.. ... ..x
.x. ... .x.
..x ... x..
... x.x ...
... .x. ...
... x.x ...
..x ... x..
.x. ... .x.
x.. ... ..x


This has probably been discussed before somewhere.
Moschopulus
 
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Re: A Diagonal 17

Postby Red Ed » Sun Nov 06, 2005 11:03 am

Moschopulus wrote:Is there a puzzle with 17 clues where all the clues are on the two diagonals?
That's ambitious -- we haven't even found any rotationally-symmetric (in the position, not value, of the clues) 17s! Has anyone checked Gordon's huge list to see if any of those have the X factor, I wonder?
Red Ed
 
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Postby gfroyle » Sun Nov 06, 2005 11:19 am

None of the existing 17s are diagonal..

I *think* that I have searched exhaustively that pattern, subject to the restriction that no digit occurs more than 3 times, without success. But (as usual) I have not kept rigorous records of exactly which searches I have performed, so there is a slight chance that I am mis-remembering...

In fact, none of the existing 17s have rotational symmetry. I recently got an email from someone who says that his program takes only 2.5 hours to completely examine a 17-clue pattern. If this is true, and he has not made any hidden assumptions, then it would be feasible to check exhaustively all rotational 17 clue patterns.

Cheers

Gordon
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