Sue Defeats the Slippery Wex 428


wex 428 basic trThe third Weekly Extremes review puzzle is another rewrite, in which an extreme level pattern analysis is made unnecessary by an advanced technique overlooked at first reading.

Taxes in? On the review, Wex 428 was easy on us through basic solving. A very generous slink bypass gave us quick box marking and very moderate line marking, with a naked triple to keep us awake.

Again, a potential Sue de Coq on the line marked grid appears, taunting me for missing it before. I kinda’ hope it doesn’t erase the coloring cluster extension via pattern analysis I was planning on.

wex 428 basic grid sdcYou have the verification dance by now. The chute is

SWr9 = 5(1+9)(7+8),

or 5 plus naked pair 78.

If (1+9) is an alternate, so is (7+8). But if it’s missing, the two cells in the remainder of r9 can supply the 1 and 9. But if it’s not missing, we can discard the possiblility of a naked pair 78. Then bv19 has to supply 1 or 9 needed in the chute, and 9r9c5 will never be a clue.

wex 428 trial tr 1So I scratch out a trial trace of SWnp78. It’s a long and tedious one, with a consolation prize in the middle, the naked triple(nt).  Whdx9m,  stands for “hidden dublex=>W9m”. My hidden dublex is a form of double line exclusion. See Sysudokie Speak.

wex 428 trial gridThe trial would have bogged down without the naked triple.

The SWnp78 is found guilty to a charge of forcing two 7’s into c6.

wex 428 trial tr 2Regular readers may be scratching their heads, but a trial trace can be divided like that because it is breath first and is read line by line.

wex 428 XYZ remote pairNow 428 comes apart, as a direct consequence of that 9r9c5 removal. A grouped forcing chain (or ER wink) creates a remote 798-wing, but there are no victims. However, a parallel 8 forcing chain completes a remote pair pair, a.k.a conjugate pair, removing 7r8c6 and confirming 7r3c6 as N7. I wasn’t even aware that could happen!

Listen up, WECer friends: Such revelations happen when you work advanced techniques at the fundamental, sysudokie level. Don’t bypass these catches  by guessing! Well, not after your WEC solution is submitted, anyway. Do you have that grouped forcing chain thing down?

wex 428 kraken swordWex 428 has a pretty final act. My 9-panel now reveals a kraken swordfish. The victim sees the fin via an XY forcing chain.

The collapse follows immediately. I’m showing the trace to give you another example of a regular 2-D trace. Unlike the trial trace, all consequences of a cause is explored before the next cause its effect list is explored. Its depth first.

wex 428 final trBoth traces are left to right, but in the regular trace, unused causes sprout out of a descending leg to start their own descending leg.

The review continues next Tuesday with Wex 429.

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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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