Solving The Golden Nugget


Just in time for New Years, the Golden Nugget falls on the fourth exocet trial.  The monster gets creamed by the convergence of three powerful, but entirely accessible sysudoku tactics:   exocet trials, enumerated and sliced patterns, and the Sue de Coq verification trial.

gn exo 24 loopHappy New Year, readers.  I hope you got involved, and into the dog work of the first exocet verifications  of mid December, and first three exocet trials of the Christmas eve post, because otherwise, the finish is going to look deceptively easy.

Continuing the 24 base solution from the earlier post, there are four possible subordinate trials implicit in this grid. One dimension is the base order, and a second, independent choice is the loop direction.

gn exo 24 SdCsI left the base order undetermined, and chose r4c8 = 4, the  counter-clockwise loop direction at that cell. In the resulting grid, a pair of Sue de Coq co-operate, namely

Nc6 =1(6+8)(7+9)+719

and

Cr3 = 9(3+5)(1+7)+197.

At least  one must be valid, since the “bv missing” values clash.  I take Cr3 to try first.

gn exo 24 197And the trial runs out of gas without contradiction!  I might be stuck, but the 2-brigade arrives with good news: 

gn exo 24 patsOnly two 2-patterns fit on the grid! The solid Olive1 blue and and the dashed olive 2 blue.  My choice was  to try the candidates common to both patterns, or to try the entire patterns.  I went with that.

Olive 1 failed in “almost” fashion.  I had to be ready for Olive 2 to fail, and to move on to the 27 and 47 exocet trials.  This time, it was Golden Nugget that surrendered.  The trial traces are below.

gn final trace 

 gn exocet solutionWith the solution, I want to include reminders of the human solving route that took us there.  The true candidates are shown in the pencil mark font of the trials.  Add the freeform of the true 2-pattern,  and the chute of the failed but decisive  Sue de Coq.  And to accompany the target cells of the exocet,  add the links of the AIC nice loop of the trial solution that was found to be the Golden Nugget solution.  This grid is my momento of a human solver triumph.

Of course we have not shown that the Nugget has but one solution, and many forks along the road were not taken.  But my Golden Nugget presentation that tracks this solving has 42 slides!  A monster puzzle is in many ways a collection of puzzles in itself.

This is the last Tuesday, and the last post of 2013. I’m looking forward to another year of Systematic Sudoku blogging.  Expect occasional announcements of improvements in pages and earlier posts, with back links. To posts introducing concepts, I’ll be adding comments linking forward to examples in later posts. There will be more reviews of tough puzzle collections, more explanations of promising techniques, and yes, more monster assaults.  And who knows, maybe your helpful comments. I hope you’ll find the back posts informative and entertaining, and will be here with me on 2014 Tuesdays.

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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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