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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

 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. Y-Chain 1: Load Example or : From the Start

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## 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