Tough, But Not So Nasty


Continuing with the review of Frank Longo’s The Nastiest Sudoku Book Ever, a sysudokie faces another hard judgement on a Single Alternate Sue de Coq, in Nastiest 662. If the trial is archived, the puzzle withstands major blows before giving up, and delivers much needed WXYZ-wing along the way.

Or so I thought. No sooner had I posted my “gem”, when two of my backup buds, Gordon and StrmCkr, alerted me to a flock of X-wings overlooked in line marking. Sad to say, the WXYZ got squeezed out. Not to be completely outdone, however, I duck taped it to the end of this revised post.

nastiest 662 LM wingHere is the grid at the first 1-wing in the basic solving trace below, right after the naked triple in c4.

You, too, can join my backup/ mortification team by copying the Calibri scripted givens on an early grid. Or just point out the gross error at any stage. You don’t have to pin down how I got there.

nastiest 662 basic trLooking at the whole basic trace, Nastiest 662 starts off generously, then turns a little stingy.

Right after the 1-wing, the 4-wing r68c29 clears out 3r1c2, 4r7c2 and 4r7c9. Follow up marking does a box/line wipe out of 6r1c2.

 

 

nastiest 662 sasdcLine marking is followed by the Single Alternate Sue de Coq

SWc2 = 6(2+4)(1+9) +  196.

The trial of SWc2 =196 results in an “obvious” forcing of two 4’s in c8.

This verifies the

Sue de Coq

6(2+4)(1+9).

The removals bring an immediate collapse, beginning:

nastiest 662 collapse trIf we archive the SASdC, however,

we get to see, not the WXYZ wing I got with sloppy line marking, but . . .

 

nastiest 662 nice loopA very productive nice loop, or two stacked nice loops, if you prefer.

 

Remarkably, in view of the quick SA Sue de Coq collapse, Nastiest 662 hangs on.

 

The naked pair r3np19 is going to remove 9r3c6, but I peeked at the 9-panel , and said, “Not so fast!

 

nastiest 662 9-panelBefore you go, your presence is required in a swordfish.” Of course, if 9r3c6 departs first, the 9-wing that remains will confirm 9r9c6 and the swordfish victim is doomed anyway, but I like to look at a swordfish when I get the chance.

Well, that did it. After a nice loop coloring,

nastiest 662 last tr

 

 

 

nastiest 662 coloringthe cluster extends out to where the blue army contradicts itself in c2, and the green army takes over. You can see it from here.

 

Nastiest 662 is done, but don’t you want to see that misbegotten WXYZ-wing I wanted so badly?

 

 

 

nastiest 662 1294 wingHere it is, a 1294 wing with an irregular victim. It is not a BARN or BNS, because it reaches outside of any bent region. The significance of that was explained in Please Give WXYZ Some Space last August, and will be explored in an upcoming post on the BARN.

The victim sees the hinge, and one of the wings, by forcing chains. Too bad it didn’t really happen.

Next time, we finish the review of The Nastiest Sudoku Book Ever, with snapshots from the final four preselected puzzles.

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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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