Revisiting Wex 435


This post updates the Weekly Extreme Review with a revisit of Wex 435, a puzzle that proved resistant to the single alternate Sue de Coq and was deemed the toughest in the review series, inspiring an extreme ALS trial, the jump ball, in the review. But afterward, two setbacks at the hand of sysudokie friend Gordon Fick enables a kraken 1-wing and two advanced level finishes, one by Gordon and another by YT.

Wex 435 UR with SdcFrom the basic grid opening the post of June 2, Gordon noted a UR removal to go with the indecisive single alternate Sue de Coq. In Fick’s UR, the floor naked pair c3np19 force one of 9r2c2 or 9f8c3 to be true. Then if either 1r2c2 or 1r8c2 is true, a deadly rectangle, and at least two solutions, occurs.

 

 

 

Wex 435 W-wingNext in the bv scan, Gordon calls upon his Hodoku training, and finds a W-wing on the 1-panel. The W-wing is described on the Hokoku wings page as a pair of identical bv with one of the two numbers linked. Hodoku over specifies the link, saying that a strong link is required. Actually, the inference logic requires a weak link is made by forcing chain or ER. A unit wink would make it a naked pair. Hodoku’s two examples illustrate the W-wing with AIC winks. I now include a W-wing schematic and one of the Hodoku examples, translated for Sysudoku readers, in the XY-chain post.  The matching bv of a potential W-wing makes it a tempting target for building AIC winks.

Wex 435 ANL krakenAlong with the W-wing, Gordon came up with a 1-chain(green) removal that pairs with the W-wing to enable a kraken 1-wing on the 1-panel.

Kraken analysis is another worthwhile occupation for forcing   chains.  Here, double chains force through a grouped chain that gives the finned 1-wing victim its fatal vision of the fin.

 

Wex 435 nt boxlineThat is followed by a NW naked triple and a NEr2 boxline. At this point, Gordon and I part company.

 

 

Wex 435 color wrapI’m attracted to the meadow of bv for the coloring. The trial trace helps me find a quick wrap in which two blue candidates are found guilty of removing all 5’s from r5, proving green.

The collapse starts with 4r4c3.

 

 

 

 

Wex 435 Ficks wicked AICGordon, on the other hand, found Wex 435 to be a playground for AIC ANL, using XY-chains extended by slinks. His first blow was this wicked ANL with XY ends and a Medusa X-chain in the middle.

I added the relevant AIC hinge that would have helped me construct such a chain. My hinge marker encloses candidates bringing slinks into a multiple candidate cell. The slink pencil marking by corners makes hinges easy find, and they help you spot AIC strong links.

Wex 435  wicked trWex 435 second W-wingAfter the follow up, another W-wing:

As Wex 435 falls back on the ropes,

 

Wex 435  AIC hidden pair

 

Gordon wades in with another AIC ANL, this XY and X-chain mix bringing a naked pair to remove 7r7c9, and leaving a hidden pair 57 in the East box.

Wex 435  hidden pair trGordon’s knockout blow was a round house AIC ANL that covered the grid, and brought an immediate collapse.

 

Wex 435  AIC knockoutBefore the collapse, I got a snapshop of an irregular remote pair, in red. The victim sees one of the forbidden ending 5’s by forcing chain.

I hope these posts have alerted some dedicated WECers to new possibilities in the competition puzzles.

 

 

 

Please comment, particularly if my review of another Competition puzzle would be of special interest to you. I’ll try to enlist Gordon to attack from the other direction.

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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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