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X Wings in a hard puzzle?

 
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George Woods



Joined: 28 Mar 2006
Posts: 232
Location: Dorset UK

PostPosted: Thu Aug 24, 2006 3:05 pm    Post subject: X Wings in a hard puzzle? Reply with quote

I know that an "advanced" technique might be useful in a puzzle that can be solved by simpler techniques. However I was not expecting X Wings in today's (24 August) Sudoku.

I solved it via 2 Xwings in 3 and one in 4, but could it have been done without using these X Wings?

Using the draw/hint program I certainly got the impression that at least one X wing was used.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Thu Aug 24, 2006 3:53 pm    Post subject: Reply with quote

George,

It is solvable without using the X-wings. There are two box/line interactions that make the same exclusions as the X-wing on 4.

I never saw an X-wing on 3 until it was solved and I back-tracked while looking at the 3's. After looking at the puzzle while focusing on 3's I only saw one X-wing (r3c59 & r5c59), it appears that the (2,3) naked pair that eventually shows up in column 9, destroys it without having to make use of it's exclusions. I did see a swordfish on 3's, but it was the complement to the X-wing.
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