Solver App for Android and iPhone
Strategies for Number Puzzles of all kinds
Page Index
Solvers
Puzzles
Basic Strategies
Tough Strategies
Diabolical Strategies
Extreme Strategies
Depreciated Strategies
Str8ts
Other

Y-Wing Chains

This strategy has been depreciated. It is a clear subset of other chaining strategies and does not need to be identified uniquely

Y-Chain 1
Y-Chain 1 : Load Example or : From the Start
The Y-Wing strategy can be extended into chains. Remember, the Y-Wing consists of a pivot cell and two pincers. We keep the principle of the pincers exactly the same. The difference is that the pivot can be replaced by locked pairs.

Our pivot chain for a Y-Wing must proceed at odd numbered cells (or even number of links). A Y-Wing is simply a chain with length = 1.

In Figure 1 we have a Y-Wing Chain marked out in green cells. The 5/7 pivot consists of three pairs of 5/7. The first 5/7 (in which ever order) is connected to the last 5/7 by a third 5/7 in the middle, and by definition this is a locked pair. If the first 5/7 is a 5 then the third one must be a 5 as well. Same goes for number 7.

Our pincer is based on the two green cells marked with a red border - the pairs 7/9 and 5/9. The principle of the Y-Wing says that any cells that both those can see we can eliminate the common number - in this case 9. The two cells marked with a red circle can be 'seen' by both and the 9 removed.
Go back to WXYZ-WingContinue to XY-Chains


Comments

Your Name/Handle

Email Address - required for confirmation (it will not be displayed here)

Your comment or question

Please enter the
letters you see:
arrow
Enter these letters Remember me


Please keep your comments relevant to this article.
Email addresses are never displayed, but they are required to confirm your comments. When you enter your name and email address, you'll be sent a link to confirm your comment. Line breaks and paragraphs are automatically converted - no need to use <p> or <br> tags.
Comments Talk

Monday 8-Aug-2011

... by: Elce

Should paragraph 2 read: " Our pivot chain for a y-Wing must proceed at an ODD number of POINTS (ie an EVEN number of LENGTHS between the points)" ?
Or have I missed the point!!
Thanks for your great tips - I am trying to use them to help me solve a hard (v hard!) samurai sudoku ie 4 sudocku with an interlocking central sudoku - any clues for this greatly appreciated!!
Andrew Stuart writes:

The old fence-post issue. I've reworded that sentence. Appreciated

Article created on 11-April-2008. Views: 70987
This page was last modified on 6-January-2014.
All text is copyright and for personal use only but may be reproduced with the permission of the author.
Copyright Andrew Stuart @ Syndicated Puzzles Inc, 2014