Almost Extreme 175 Tags Five Advanced Bases

This post reaches the halfway point in the review of Manuel Castillo’s Only Extreme collection, with Only Extreme 175. A double UR, a regular Sue de Coq and irregular XYZ-wing prepare the bv field for coloring, and an XY chain coloring wrap.

A challenging Sysudoku basic,

leads to a busy, unbalanced grid.  Advanced work begins with a Type 1 unique rectangle with two removals.  Neither victim can be present if an obvious multiplicity is to be avoided.





A rare treat is the Sue de Coq hidden in the brambles, that removes seven marks and triggers a box/line removing four more.






Manuel’s Halloween treats continue with an irregular 784 -wing.  The 7 wink attaching the 47-wing is an ER 7-chain.

Also irregular is the  4r9c2 victim seeing two of the toxic 4’s by grouped 4-chain.



The X-panels are less generous, so after a quick survey of the bv field, I get out the crayons.

My usual blue/green starting cluster is surrounded by a red/orange one when it stalls.  There are two traps.


More tellingly, in this clash of clusters, it turns out that blue and orange are incompatible. Going a little further, so are blue and red.  Since we must have red or orange, blue must go.

In logical expression this computes as:

Not(blue and orange) and not(blue and red) = (green or red) and (green or orange)

                                                                                = green and (red or orange) = green

 Two wrongs don’t make a right, but these two mismatches do make a wrap.

 Looking at the revised bv map,  there is  a long XY chain with four  removals, including a red 3.     This is a wrap by XY chain, always a possibility with coloring.    Here it starts an immediate collapse.

Next time, 43 Extreme Sudoku later, it would be Only Extreme 218, but this review is interrupted for breaking news, a report on the Akron 2017 Sudoku Tournament.  Watch this space. 



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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