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 Y-Wing Chains From sudokuwiki.org, the puzzle solver's site
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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 Article created on 11-April-2008. Views: 42459This page was last modified on 6-January-2014, at 19:19.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