Category Archives: Advanced Solving

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

ALS Map AIC building on UHC 311


This post uses the ALS Map constructed in the previous post to continue the solving of ultrahardcore 311 after the AIC building and before systematic search for ALS_XZ. The ALS map prepares for ALS_XZ, but since it’s made immediately following … Continue reading

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Dov Introduces Lite Coloring of ultrahardcore 311


This post finishes the lite coloring revisit of past trials with Dov Mittelman’s lite introduction. It leads to a solution of Stefan Heine’s UHC 311 without trial. This puzzle occupied 3 posts in the ultrahardcore review, starting with November 3. … Continue reading

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Lite Coloring Avoids Trials in KrazyDad 425


This post backs up your lite coloring effort, I hope, on KrazyDad 425. The initial lite trees deliver a cluster merge, and as these grow, lite coloring gives two confirmations and a coloring wrap to finish without trial. The first … Continue reading

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A Lite Update on Castillo’s Only Extreme 347


This post updates a solution by coloring trial in the review post of 12/19/17. A bypass of 6 4-fills resolves 3 of them immediately,  but goes no further than the original 3-fill only bypass.  Then we follow Beeby through a … Continue reading

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A Lite Coloring Update of Castillo’s Only Extreme 261


This post is the first of several which update earlier review solutions to include a new guy in town, lite coloring. The earlier posts will be left as they are, except for added links to these updating posts. Instead of … Continue reading

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An Error Hides a Lite Coloring Trap on ultrahardcore 399


This post corrects an error on the post of December 8, that prevents a lite coloring trap in ultrahardcore 399. Then there’s follow up on the trap, with the lite coloring marking in place. Trial is not avoided, but the … Continue reading

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Lite Coloring in a Red Russel Special


This post explains lite coloring as I understand it from comments and emails from its apparent inventor, Dov Mittelman. I only know Dov as a reader of this blog. He (or she) does his analysis in his head and on … Continue reading

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Ultrahardcore 91 Trials Unleash Beeby


Here is the basics launch on Stefan Heine’s ultrahardcore 91, which quickly runs my two assisting solvers out of humanly practical removals. A Single Alternate Sue de Coq  trial reduces two clusters two one, and produces  two critical clues. In … Continue reading

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Ultrahardcore 3 Falls to Coloring Trials


This post reports coloring trials that gain the solution after forcing chains when Sudokuwiki gives up.   This includes an example of a grid diagram illustrating the route to contradiction in a breath first trial trace. Then we close with a comment  … Continue reading

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An Orphan Takes Down Nakamoto Extreme 163


In this post, AIC building is replaced by BARN’s, conventional chains, coloring, and a noteworthy pattern analysis result. Nakex 163 basic starts with a 3-fill. The bypass contains six more. Two resolve into clue and naked pair, and one, into … Continue reading

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