Category Archives: Extreme Solving

Extraordinary techniques deferred past advanced ones, because of effort vs. likelihood of success.

Only Extreme 218 by SASdC Trial


This post demonstrates the Single Alternate Sue de Coq with Castillo’s Only Extreme 218. The opportunity for this kind of trial is spotted early in the bv scan, but is best deferred until it is needed as a last resort. … Continue reading

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Only Extreme 132 Joins the Extreme Team


Another payoff for expansion of a limited coloring network via AIC slink. It’s an extreme tactic that, after six years of blogging, I finally blundered my way into.  This collection illustrates the not-both trial thoroughly. Please comment if you know … Continue reading

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Only Extreme 89 Guilty on Two Counts


The Only Advanced 46 is followed by a truly Extreme 89. Two different unique Sysudoku trials lead to the same result. The Single Alternate Sue de Coq is deferred, but after advanced techniques fail, it is used.  An equally extreme … Continue reading

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AIC Slinks Finish Only Extreme 3


This post continues the finishing coloring cluster expansion in Castillo’s Only Extreme 3, via not-both testing of AIC slinks.  After extending the blue/green cluster in the North bank via AIC slink, we continue with a second AIC slink adjoining the … Continue reading

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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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