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XY-Wing limitation

 
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Marty R.



Joined: 12 Feb 2006
Posts: 5061
Location: Rochester, NY, USA

PostPosted: Mon Sep 13, 2010 3:47 am    Post subject: XY-Wing limitation Reply with quote

This topic was initiated by Doyle. W. Rausch. I accidentally deleted it while moving it to this sub-forum. Sorry Doyle.

Following is what Doyle wrote:

It seems that a unique XY-Wing solution is not obtained if the 3 XY-wing pairs are in a single line (row or column). What misunderstanding of XY-Wing criteria is involved? Or is this correct?
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Mon Sep 13, 2010 3:59 am    Post subject: Re: XY-Wing limitation Reply with quote

Marty R. wrote:
This topic was initiated by Doyle. W. Rausch. I accidentally deleted it while moving it to this sub-forum. Sorry Doyle.

Following is what Doyle wrote:

It seems that a unique XY-Wing solution is not obtained if the 3 XY-wing pairs are in a single line (row or column). What misunderstanding of XY-Wing criteria is involved? Or is this correct?

If you have ZX+XY+YZ in three cells in the same row/column/box, then it's a Naked Triple and any eliminations should have been performed prior to reaching the XY-Wing technique.

Yes, it's still a Naked Triple if you have ZX+XZY+YZ in three cells of the same house/unit. So the same holds true for an XYZ-Wing.
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