Stephens’ Extremes Snaps II


Here we continue with snapshots from the review puzzles from Stephens’ The Sudoku Addict’s Workbook.  The review covers 10 of 40 “Extreme” puzzles in this and Paul’s Mastering Sudoku Week by Week. The Extreme collection is highly recommended, even if sysudoku methodology  is preferred over Stephens’.

Addicts 126 XY 1ANLThe first order of business is the mystery puzzle of the last post. What is going on? It’s Addicts 126. The 136-wing victim “sees” the 36-wing via a forcing chain.  Its removal implies SW6 which destroys the UR  r29c23.

This clue is followed by the XY ANL and 1-chain ANL shown here.

 

 

Addicts 126 coloringFollow up and coloring brings the extension of the single cluster to a wrap, driving two green candidates into cell r6c2 and confirming blue.  That also wraps up Addicts 126.

Next in the spotlight is Addicts 134. This one stubbornly resists a single clue in box marking, which must be pretty discouraging in Stephens basic.  Then it makes up for it with a naked triple and two naked singles.

My favorite part is the rare forcing chained together XYZ-wing that devastates the puzzle.

Addicts 134 fchained XYZYou might have thought  that the X and Y wing candidates of the XYZ wing must be in a unit with their partners in the hinge, but the fact is, “seeing” their hinge partners by any means is good enough.

In this case, one wing is glued on with a forcing chain.

This Frankenstein 123-wing that easily removes the victim.

If you need a trace to see how the removal collapses Addicts 134, I’ve got one for you.

Addicts 134 trace

Catch your breath.  Addicts 138 is another joy ride.  

Addicts 138 XY f1-wingThe party starts with a wild XY-chain, and continues with a finned 1-wing.  Then a simple 3-chain removes the 3-candidate in r7c7. You could follow up on these removals to find that one.  I’ll save it for the next post.

Or you can work back from the next grid coming next week in the third and last of the Extreme snaps posts. It is a Medusa coloring  of particular interest.

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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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