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 pattern-based trial duplicates the solution.

Sysudoku basic is routine, with two 3-fills in the bypass, and a box/line in line marking close.

 

 

The only bv scan result is an SASdC, a single alternate Sue de Coq describing SWr8 as containing

SWr8 = 8(2+3)(5+7) + 832.        

That is, 8 and

2 or 3 and 5 or 7

or 832.

 

 

The idea is that if it isn’t 832 then the 2+3 alternate must be supplied by  r8c4. I look for Sue de Coq early, but defer any trial (832) as a last resort.

With nothing else in the bv scan, I go to the X-panel and find a finned 1-wing. The other two victims do not “validate” their removals by “seeing the fin.

 

 

 

 

 

Coloring is a bust so far, but just to show that I’m working hard, here is the grid marked up with AIC hinges. These encircle candidates of a non-bv cell that are strongly linked to the outside. You can see how I’m trying to link them up with slinks, so that the hinge weak links create AIC segments. No cigar this time.

 

While giving me zilch on X-chains and fish, the X-panel did uncover pattern analysis opportunities on the 2 and 8 panels. Both have that little slink corner that limit available patterns described by freeforms.  Starting from the West side of the 2-panel, there is only one freeform from r9c3. I colored it blue, and found enough freeforms from the other candidate to be sure there are no orphans.

Now coloring on that basis, either the blue pattern is true, or one of the green patterns is. We have a second trial.

Are we at last resort time? If so, which trial is better? If right, the wide ranging blue pattern trial is likely to produce the steeper collapse.  On the other hand, those two-clue combination trials of the SASdC are often decisive. But no worries, we have both.

First come, first served, the trial of SWr8 = 832 reached a contradiction. To suggest the comparative difficulty, the trial trace is above.

So now the regular Sue de Coq logic becomes effective. Its removal collapses Only Extreme 89. This is a regular depth first trace, not a trial trace, because it is no longer seeking to pinpoint a contradiction, but going for the solution.

As for the blue pattern trial, there is little left after the blue candidate’s effects are recorded on the grid. But if you’re from Missouri, and you want to be shown, note here how easily the blue pattern generates the key clue, S5. You know what happens then.

Next time it’s the fourth review selection, Only Extreme 132.

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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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