Departing Highlights on Bean’s Extremely Hard Sudoku

It’s time to wind up the volume 10 review, with a few highlights behind the review table.

The first one is the very unusual basic trace of IV-12, the homework puzzle of the previous post.

You have the characteristic Extremely Hard stinginess in the bypass, then a near collapse in the 1: list in box marking, with normal box marking completing the collapse. The 3-fills are plentiful and decisive.

Here’s the grid as box marking resumes.





Along with bypass solutions, here is something else an Extremely Hard collection should avoid: a routine basic, and a solution by means of:

a regular 475-wing, rare, but not extremely hard. That’s in Extremely Hard 10 I-3.

The Guide explains when this happens and when it doesn’t.

Then capper in I-3 is a 5-chain skyscraper.

The collapse begins with C5.







Extremely Hard 10 IV-47 is another puzzle embarrassed to be found in an Extremely Hard collection.  Advanced fun starts with a remote pair that’s hard to miss.





Next, another regular 251-wing. The grouped 1-chain victim is advanced level hard, but hardly extreme. The knockout blow for IV-47 is a short XY-chain ANL.




And finally, there is Extremely Hard v.10 VI-9, starting with a beautiful spiral, . . .

. . .and moving, Hodoku batting cage style, to a remarkable nice loop, which triggers the collapse inducing 1-wing.



In closing this review of volume 10 of Rebecca Bean’s Extremely Hard Sudoku, I recommend its highest ranking puzzles as an advanced collection, with the possibility of an extreme challenge.



Next week, as part of a progress report on the Sysudoku Guide, checkpoint your solution of Andrew Stuart’s fourth and most challenging example in the WXYZ-Wing page of the ‘Bent’ Sets section of his Strategy Families page. In case you don’t want a peek at his example first, here is the starting grid.


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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