dailysudoku.com

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

Are the VH's getting easier, or have a learned something?

Today's VH had parallel pairs in columns 4 and 6 of rows 1 and 5,
requiring a 2 in R1C4, and rest was simple elimination.
Or was I lucky?

Earl[/b]

jLo · Joined: 30 Apr 2007 Posts: 55

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

jlo,

Would you please show me the W wing.

Earl

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Hi Earl - it would be helpful if you could paste the grid. Marty has left some instructions in the Site Help forum.

jLo · Joined: 30 Apr 2007 Posts: 55

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

Yes it did seem easy. There were a couple of obvious x wings on 7's and 5's - and a Unique Rectangle of three 15's and a 152 on rows 1 and 5.

Where can I find an explanation for this W-Wing thing. I've been avoiding it because it seems to be a recent and contrived innovation. X,Y,Z are logical coordinates. W ain't.

Marty R. · Posted: Fri Jun 22, 2007 12:05 am Post subject:

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Could the W-wing be a variant on remote pairs ?

Steve R · Posted: Fri Jun 22, 2007 11:23 am Post subject:

I think it’s a matter of how broadly you want to look at it. As I see it, both are examples of double implication chains (= nice chains) with bivalue cells, say [xy], at the ends:

[xy] -x- a … d -x- [xy]

Because the labels at the ends are the same, here x, and both end links are weak, y may be eliminated from any common associate of the end cells. This applies irrespective of the links between cells a and d.

The distinctive feature of remote pairs is that all the nodes are of the [xy] type and all the links are weak:

[xy] -x- [xy] -y- … -y- [xy] -x- [xy]

In the case of the w-wing it is the shortness of the chain and a single strong link:

[xy] -x- a =x= b -x- [xy]

These characteristics make the patterns relatively easy to spot and use. I find a w-wing more quickly than an xy-wing but that may be because I rarely use pencil marks in intermediate puzzles.

Steve.

Mogulmeister · Joined: 03 May 2007 Posts: 1151

Thanks Steve - it does depend on how you look at it.

The other thing more simplistically, is that the human eye is probably more easily drawn to pairs in the W-wing (even in different boxes) than the three bivalues in an X-Y. In an X-Y wing you still need to find all three bivalue squares to be sure that you have one.

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

I went back to look at the post explaining W Wings - like I was told to do (above). Found the first few posts confusing but kudos to TexCat for putting everything into a easy to follow diagram. (though still can't figure why he uses letters GW to denote a pair)

Also still not clear in above post from JLo how he eliminated the 2 from R3C3 to get a 14.

Steve R · Posted: Fri Jun 22, 2007 6:05 pm Post subject:

I think this is the position you are referring to.