Master Class 120 Completes the Update

This post concludes the review update of Tom Sheldon’s Master Class Sudoku and offers an amended review table.

The bypass on Master Class 120 is strong enough to keep line marking fill strings short. There are two naked singles, one springing a grid clearing breakout.



The bv scan picks up a Type 1 hidden unique rectangle immediately after line marking.

From the corner opposite the one free of extra candidates, two slinks in UR value 7 lie along the sides of the rectangle. If the UR partner value 9 in the opposite corner is true, the  7 candidate is not, and slink value 7 is forced in the adjacent corners. The remaining corner is 9.

In the placed rectangle,  the UR values in the corners can be interchanged without affecting any other cells, for a second solution.

In the original review’s highlights post,  a DIY UR analysis generates an additional removal, along with a swordfish.

This time, we add an XY extension to the original ANL for a quick collapse of Master Class 120,  starting with the trace below.










The table for the updated review of Master Class Sudoku  follows the plan adopted after the original review in which the results of applying the Sysudoku order of battle is reported in detail for every review puzzle.

Only the last two review puzzles survived Basic, but none fell victim to the bypass. Two additional puzzles, 130 and 140, were included in the table to suggest that the shift to advanced level was not by chance, although it was not mentioned by Sheldon.

Next, we take up another collection, just recently out, that is half basic level and half advanced level. Unlike Master Class, there is no trend, and you don’t know which level the next puzzle is in. I’m going to refer to this collection of unacknowledged authorship as FTSPAH, in place of the full title, which is F*CK! These Sudoku Puzzles Are Hard!

Before These Puzzles, however, you might try your Basic on a Dave Green Sunday 5-Star that thumbs its nose at the bypass, and comes very close to breaking through Sysudoku line marking into advanced territory. Regular readers know I have been featuring the Conceptis Sudoku puzzles from the Akron Beacon Journal, for 9 years.

Here is the puzzle in question, from The Beacon Journal Sunday 9/15/2019. My first solution featured a unique rectangle, a BARN, and a naked triple, but omitted critical moves. Correcting these, the 5-star grid reveals why it is such a challenge.

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.
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