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keith · Posted: Sun May 16, 2010 8:27 am Post subject: BB May 15, Super Hard

I enjoyed this VH:

Marty R. · Posted: Sun May 16, 2010 5:18 pm Post subject:

BBs seldom need five moves, but I just played whatever caught my eye.

XYZ-Wing, Type 2 UR and three XY-Wings.

peterj · Joined: 26 Mar 2010 Posts: 974 Location: London, UK

I took the easy x-wing(2) and followed with a couple of xy-wings - 269 and 789.

Other than the x-wing there seemed to be very few single digit steps - an x-cycle on 2s but it didn't help very much

Mogulmeister · Joined: 03 May 2007 Posts: 1151

That looks optimal to me Peter. I looked at various ANPs and at one point a large finned fish but kept coming back to the x-wing and xy wings.

cgordon · Joined: 04 May 2007 Posts: 769 Location: ontario, canada

There was also a Type 4 UR for 16.

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Yeah - saw that but it really doesn't alter the price of eggs in this puzzle.

tlanglet · Posted: Mon May 17, 2010 10:32 pm Post subject:

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Nice double Ted. that (69=5) is so tantalising - when you reach the
(6=2)r5c8 in one sense you have a solved puzzle but......

storm_norm · Joined: 18 Oct 2007 Posts: 1741

since no one pointed them out yet.
there are some singles chains on 6.

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Thanks Norm for the nice diagram and a wonderful demonstration of strong links and their extension.*

As two strong links both share the same house/stack/band in b1 then r2c7 OR r7c2 is true for 6. These are "pincers". In those positions however, nothing is eliminated because there is no 6 at r7c7.

However when we extend (or transport)by following the chain from r2c7 the pincer there is extended to r9c9.

We now know that either r7c2 or r9c9 is true for 6 and we can therefore eliminate 6s at r7c8, r9c13.

*With apologies to all you who know this stuff but I thought it might be helpful to any who "drop in" in the search for knowledge.

daj95376 · Joined: 23 Aug 2008 Posts: 3854

Norm's chain performs all three eliminations at once. For those who may be wondering if a fish pattern is available, the answer is a qualified yes. There are strong inferences in [r2] and [c2], and a grouped strong inference in [c9]. These three houses/units/sectors form the base set for each fish. The cover set uses houses/units/sectors [b1] and [b3] in both fish, with [b7] and [b9] being alternately used to complete their cover sets.