LPO Knocks Out World’s Hardest 36


A challenge posed by The Worlds Hardest Sudoku Book 36: Is there a route to the solution less advanced than pattern analysis? The puzzle is otherwise distinguished by a BARN right out of line marking, and a notable lack of givens information on the placement of 6’s.

The basic trace is too simple for comfort.

 

 

 

But it is delightful in brain based solving, as it closes with a BARN similar the one in Stuart solver analyzed 200.

 

 

Frustration followed, as none of the usual advanced methods advanced the cause, until . . .

looking along the edges of the panels, this elimination emerged from the top down freeforms: no 5-pattern can contain 5r1c9, because no freeform starting there can make it to r8.
Then I noticed the sashimi swordfish claiming the same victim. The finned fish works because the victim is in the fin box.

 

 

The resulting NE5 creates to final slink in the 9-chain ANL, and collapse follows.

 

 

 

 

 

 

 

Next is World’s Hardest 65, another 0.91. World’s Hardest Sudoku is not being hard enough. I’m trying to work in some UPE and ALS where they fit. Tell me what I’m missing.

 

 

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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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