Longo’s Nastiest Ever After

This post finishes the illustrative review of Frank Longo’s The Nastiest Sudoku Book Ever, with review puzzles 673, 684, 695 and 706. The bv scan and occasional easy coloring continue to be enough for what Frank claimed to be the toughest part of this not so nasty, but entertaining, collection.

nastiest 673 UR 1 and 2Nastiest 673 catches a nasty case of Type4 Unique Rectangle. One of the worst I’ve ever seen.

On the left, the 3-slink prevents any UR partner 4 from its corners, bringing in two more bv.

In the middle, the 5-slink throws out the only two 6’s in c4 outside of the N box, for a boxline removing two more.


nastiest 673 UR 3, nice loopThen as the dust settles, another UR emerges, obviously requiring the presence of 9r1c8. I include the magic top hat nice loop that I thought would be important, but now it only marks the raging path of the collapse.

See a doctor about that nasty UR infection, Frank.




nastiest 684 easy extended UROut of line marking, Nastiest 684 only needs 7r7c8 to prevent an extended unique rectangle and collapse the puzzle.








nastiest 695 sasdcNastiest 695 followed the recipe closely. An X-wing in line marking, and a definitely obvious Single Alternate Sue de Coq.

A regular 485-wing triggers a boxline for two more removals.


nastiest 695 fin fish XY ANLThen an XY ANL and the review’s only finned fish with a fin box removal.










nastiest 695 coloringWhen a large bv field brings out the crayons, two clusters are laid out. Two blue candidates land in the same cell, and get their clan ejected. Green then implies red and 695 is history.

On the battle field, you can see it all from here.





nastiest 706 259 wingThe party ends with Nastiest 706 with two Single Alternate Sue de Coq’s archived. A 259 wing enables . . .








nastiest 706 XY ANL. . . an XY chain ANL (black)to remove 1’s.  A 12-wing (purple)removes 9r3c7, but not before another victim sees a wing of the 12-wing by forcing chain(red) through it. The collapse follows promptly.

From this pre- selected set of puzzles from Frank Longo’s The Nastiest Sudoku Book Ever , its fair to say that the book falls a bit short of the title.

However, that’s what we have come to expect from Frank, a ringmaster of the Sudoku circus. At least all of the reviewed nasties get into advanced technique, and with entertaining results, and basic solving is not difficult. This may be just what you want.

Next post, I return to the bent N-set methods to revisit the remarkable BARN, and tell how it was constructed by the equally remarkable StrmCkr, from timber cut by the Sudoku sage, Andrew Stuart.


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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