Category Archives: Advanced Solving

Techniques applying after candidates are identified. Why they work. How and when to look for them.

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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Cluster Extension by Not-Both Trials


In this post and the next, the first puzzle of the Manuel Castillo Only Extreme Sudoku review, Only Extreme 3,  is taken ahead of the review of his Only Hard Sudoku. The reason is in the title. Rounding out the … Continue reading

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Badger’s Advanced Sudoku


This post highlights David Badger’s two advance puzzles in the Sudoku 1001 Hard Puzzles sysudokie review, both starting with the almost nice loops to be found along the XY railway. In 301, the black XY ANL removes two 7’s, and … Continue reading

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A Bifurcated Coloring of the AIC Slink


In this post, the AIC slink produces an alternative solution of a puzzle originally solved by a rather extreme pattern coloring analysis. This solution demonstrates how the AIC Slink enhances the already powerful technique of Medusa coloring. The July 11 … Continue reading

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Two of Rebecca Bean’s Less Extreme


Here the Rebecca Bean Extremely Hard review closes with a line marking finish and an easy coloring. The collection is far from extremely hard, if the sample of 12 pre-selected for this review is typical. On the way to line … Continue reading

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Bean’s Extremely Hard I


A review of Rebecca Bean’s 600 Extremely Hard Sudoku Puzzles with Answers begins with the review table and two puzzles, 7-6 and 12-6. The collection is mostly basic, with the half of them solved by the slink marking bypass. Puzzle … Continue reading

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Slink vs. Coloring Networks and Illogical Sudoku


This post reports a surprising fact about multiple solution puzzles, that solutions found by backtracking tree search can be logically inconsistent. Specifically, such solutions violate the coloring network implied by the givens. I happened on this fact by means of … Continue reading

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