An Ardson Very Hard Workout

This post checkpoints Ardv2 78, the second review puzzle in A.D. Ardson’s Sudoku Very Hard collection. The puzzle skates by basic and the bv scan, but is tamed on the X-panel.

Along with regular collection reviewing posts, I’m revising the first year’s posts 2011-2012 to bring graphics, tracing and solving examples up to date.

The naked triple occurs on the closure of columns.

On the update, Beeby finds a very obscure hidden unique rectangle.

The next point of interest in Ardv2 78 is its remarkable resistance to the bv scan, with such a rich bv field.

. Here almost all of the duplicated candidates are in the same unit, and the corresponding slinks call for the X-panel and the crayons.

On the X-panels, a 4-panel slink chain allows itself to be interpreted as an AIC, for another removal.

Then comes a Sashimi 8-wing with a double fin.

On the first cluster, the 4- chain removal is duplicated and a second 4-chain becomes a coloring trap.

The second cluster makes a shortcut to a second removal, across clusters. That allows a third 4 ANL to start at 4r7c8.

The expansion slinks red and green 4-candidates in r7 and the SE box, merging the clusters. The merge brings two more traps, and a green wrap in c8.

The extensive cluster tells you something about why 78 is “very hard”. A large region of the grid is dominated by blue/green bv. This region can’t distinguish between two solutions.

Did an Amazon drone fly in the window with your volume 2 of 400 Ardson very hard Sudoku puzzles yet? If not, here is a copy of Ardv2 118 for next week.

About Sudent

I'm John Welch, a retired engineering professor, father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. Sudoku analysis and illustration is a great hobby and a healthy mental challenge.
This entry was posted in Advanced Solving, Puzzle Reviews and tagged , , , , , , , , , . Bookmark the permalink.

2 Responses to An Ardson Very Hard Workout

  1. dovmittelman says:

    Maybe I’m just being dense, but where’s the c1 3-slink? You have rows 6, 8, and 9.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s