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dongrave · Joined: 06 Mar 2014 Posts: 568

There's also a 347 XYZ Wing with pivot at r7c5 (-3r7c4) that solves it. (The 3 X Wing in rows 4 and 7 does not.)

Earl · Joined: 30 May 2007 Posts: 677 Location: Victoria, KS

UR34 in R4C4,R6C8 by 4s in R9, -3R4C7

Early Earl

dongrave · Joined: 06 Mar 2014 Posts: 568

Hi Earl, I don't completely understand your solution. Is it saying the same thing as something like (3=4)r6c8-r9c8=r9c4-(4=3)r4c4 => r4c7<>3. Thanks, Don.

immpy · Joined: 06 May 2017 Posts: 571

There is an identified UR (or Uniqueness Test type 1) (34) r47c47; but it occurs in four boxes (b5689) instead of the more standard two-box occurrence. Standard application of the technique would be that r7c4<>3,4(=2!); but that is not the case here. I have seen multiple occurrences of this 4-box UR, and in every case the extra candidate (in this case 2) can be eliminated from r7c4. This solves the puzzle easily, albeit without proper logic, as I have been told. Either of the XYZ-Wings work just as well and fit logical parameters.

cheers...immp

dongrave · Joined: 06 Mar 2014 Posts: 568

Thanks for the input immp!

I was confused by Earl's post because I know that the standard UR type 1 has to have the 3,4 pairs in exactly two boxes but as you mentioned this one has them in four (so it's not a 'standard' UR type 1). But then I noticed that he included the phrase 'by 4's in r9' so I was wondering if this was somehow a 'transported' or 'enhanced' UR of some sort because he did not come to the typical UR conclusion that you mentioned (i.e. r7c4 <> 3,4=2).

Thanks, Don.

immpy · Joined: 06 May 2017 Posts: 571

You're welcome dongrave.

Yes, I'm a bit confused by it as well. The only way I can see to make use of the 4's in row 9 is to identify the Skyscraper with the 4's in row 4; and thus r6c8<>4(=3!) and r7c7<>4(=3!). This would solve as well.

cheers...immp