Tag Archives: hidden UR

A Classic Insane 144

After the two Basic level 96 and 120, James Forest’s Classic Sudoku comes back with one puzzle, 144,  in the tradition of the KrazyDad Insane collection.  The bv are there, but it takes a few X-chain ANL to jar loose … Continue reading

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Insane 435 By Irregular XYZ and ANL

The third puzzle in a review of the KrazyDad’s Insane collection, Insane v.4, b.3, n.5,  succumbs to bv scan removals.  Some a bit unusual, but no new  ground broken.  The collection resides at http://www.krazydad.com . The updated basic trace includes … Continue reading

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Beyond the Rectangle

The alternative deadly uniqueness formations of the Sudocue Guide are detailed in this post.  Also, there is a UR checkpoint on Sheldon’s Master Class # 3 that goes beyond the UR cases surveyed in recent posts. I can’t leave the … Continue reading

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Stuart’s Hidden UR

In Logic of Sudoku, Andrew Stuart describes a unique rectangle with only one bv corner.  The tell-tale naked pair is not there.  Stuart calls this formation a hidden UR, with good reason.  You have to find the bv candidates in … Continue reading

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