An Insane 445 Pattern Slicing Demo

In this revised post, difficult line marking leaves a semi-monster. It is whittled down to a decisive double ANL, which can be duplicated instructively by pattern slicing.  The review puzzle, Insane volume 4, book 4, number 5, with thousands more, is available at .

The updated basic trace leaves two unresolved box 3-fills in the bypass.The bv in the Southwest signal a lot of possibilities.



On the line marked grid, the preponderance of candidates {12367} is striking. The bv in the Southwest signal a lot of possibilities.






Interesting but useless, is a classic, but dead 5781 wing. Put a closed curve around it, and it’s a 4-set BARN or BNS1, likewise with no victim.

But the bv do produce an APE, limiting cells r9c13 to

17 + 57 +71.


Or, the same effect is achieved by an XY wing or an enclosing 3-set BARN. Or how about another hidden UR?

The removal of 7r9c4 by  SW8 =>S8 => SWr9 boxline => S7m.




This allows a rare single alternate Sue de Coq, where the contents of SWr7 are described by   SWr7 = 69(1+5).  Since the SW ALS r9c13 must also contain 1 or 5, 1r8c3 is removed.


is the follow up.




Now, on the X-panels, a grouped 3-chain comes first.






Then a 6-ANL, plus extension to another, triggers a collapse, spoiling the pink/olive analysis of the original post.








However, for the Guide, the pattern slicing is an alternative to the double ANL.

On the 6-panel, in the freeforms going  North from r7, olive must go to r6c1, making it, and r5c3, collectors. It’s the last chance for a 6 in c1.

Now on r5, the alternatives to c7 must cross r3 at c8, a column already taken.




Since r5c3 is a pink collector, the alternatives become orphans, 6r4c4 is confirmed as placement C6, which is enough for the collapse. As r5c7 is identified as an olive collector, pink has competing collector freeform until the collapse gobbles it up.

Pattern slicing is not essential  in this solution, but Insane 445 shows how it can unravel a formidable cloud of candidates.

Four down without a guess!  But I have a foreboding  that the Insane collection is setting me up, and my surfing wave may be about to break over sharp rocks. The Insane review continues next week with Insane 455. Look it up on KrazyDad, work out the basics and be prepared to drag me out!


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.
This entry was posted in Advanced Solving, Extreme Solving, KrazyDad, Puzzle Reviews and tagged , , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s