Classic 216 Bypassed and Only Extreme 132 Demoted


This post adds another bypass solving to the review of James Forest’s Classic Sudoku, Classic 216. Then a report on an update of the 10/24/17 post on Castillo’s Only Extreme 132, in which a hard, but indecisive not-both trial leads only to another trial based on pattern analysis. In the update, a more direct application of the pattern results, along with some remarkable coloring logic, reaches a solution without trial.

First, the bypass trace of Classic 216:

Get out a grid, copy in the givens from the previous post, and account for every move. The 3-fills are signaled by square brackets. Its challenging and worth it.

Now for Only Extreme 132, the critical pattern analysis occurs on the 7-panel, where freeforms from r1 enumerate three patterns. Orange and red colors are assigned, because coloring the single pink freeform red and the candidates common to the two olive freeforms orange, we have a second coloring cluster. An immediate benefit is that three orphans are eliminated.

 

 

Back on the grid, the new red/orange cluster undergoes a very unusual wrap. The intersection of clusters in r1c4 shows that red implies blue. But in the south tier, a red 7 and Sudoku slink marking would confirm 6r7c8, implying not blue. Red cannot be true, therefore orange must be.

 

 

 

The resulting expansion of the blue/green cluster  brings a productive XY chain, but the lesson here is how the remaining candidates of the two orange patterns form a third cluster, immediately wrapped for an immediate collapse. It’s all traced and displayed in the updated post.

 

 

 

Next up is the conclusion of the Classic Sudoku review, with Classic 240. Following that is an update of the post of 11/08/17 in which a Not-Both trial, with help from pattern analysis, reaches a solution of Castillo’s Only Extreme 261. In the update, the same pattern analysis rescues a Sudokuwiki impasse to solve 261 without trial.

About Sudent

My real name is John Welch. I'm a happily married, retired professor (computer engineering), timeshare traveling, marathon running father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. The blog is about Sudoku solving. It covers how to start, basic solving to find candidates efficiently, and advanced solving methods in an efficient order of battle. It is about human solving methods, not computer solving.
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