Category Archives: Berthier

Denis Berthier in Hidden Logic of Sudoku

A Closing ALS Postscript on THLS


This post demonstrates ALS-XZ as an alternative to hidden XY chains, and concludes the review of The Hidden Logic of Sudoku by Denis Berthier. In THLS, Denis goes outside the Royles 17 collection only a few times for illustrative examples. … Continue reading

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Berthier’s xyzt Chain


This post concludes my reading of Denis Berthier’s The Hidden Logic of Sudoku, with two example puzzles to illustrate his xyzt-chain. While it is good to be aware of Berthier’s “t” versions of classic XY chains, I don’t recommend a comprehensive … Continue reading

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Berthier’s xyt-Chains Rated Extreme


This post suggests a limited role for Denis Berthier’s xyt chain in human solving. I found no THLS examples of longer chains not requiring prior xyzt or hidden chains.The last prospect, Royle 17-33442 proves to be both unjustified and unnecessary. … Continue reading

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An xyt Color Wrap


In the spirit of Valentine’s Day, I come across a coloring resource in Berthier’s xyt chain. The elaboration of Royle 17-20565 in Chapter XVII of The Hidden Logic of Sudoku is a challenge in itself. By the theory of looking … Continue reading

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Berthier’s xyt-chains in THLS


Next we review the introduction of xyt-chains in The Hidden Logic of Sudoku. These are modified XY-chains which allow extra candidates in the chain cells, and unlike regular XY-chains, make eliminations regardless of whether the chain starting candidate is true … Continue reading

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A Chicken Chok’in Checkpoint on Unhidden Chains


This post checkpoints Royle 17-16774, a rare example in The Hidden Logic of Sudoku of conjugacy chains dealing with a monster cloud of candidates. The checkpoint also catches SudoRules dismembering a “useless” XY nice loop that somehow sneaked into THLS. … Continue reading

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THLS Limps In On Chains


This post identifies the conjugacy chain, the last fundamental chain type to be introduced in The Hidden Logic of Sudoku, as a weakened X-chain.  Since the last few chapters introduce extensions for XY chains, it becomes clear that THLS is … Continue reading

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