Advancing through GM 5


This post checkpoints the bv scan and a verification of a decisive Sue de Coq in GM 5 of the Sudoku, vol.3 Grand Master collection. It also introduces GM 95, an extremely unbalanced puzzle that is due for an intense pattern attack in the following post.

Before we get started on GM 5, an announcement:  The basic solving posts of October  2011 have been revised, improving the introduction of sysudoku slink marking, box marking, line marking, and the suset subset finder to Sudoku solvers.  I hope you will read through these posts .  I’m confident they will increase your enjoyment of my blog.

GM 5 ANLOn to business, here are the unproductive wings and the productive XY-chain ANL I trust you found.  If not, you might have missed XY-chains.

Now the removal of the 7 –candidate in from the chute Wr4 leaves SdC Wr4 = 3(5+7)(2+9) with removals, provided that both 5 and 7 are not missing.

GM 5 trial traceThe trial trace discovers the contradiction of two 4-clues in r7.

GM 5 verificationThis is easily represented graphically on the grid by running a forcing chain from the grouped naked pair 9’s and an AIC from the missing 7.  Have some fun by challenging a friend to find the shortest verification path without telling them about the trial trace.  Oh wait, you’ll need to explain the full Sue de Coq theory to them first.

The verified Sue de Coq removes three  7-candidates , triggering the collapse of GM 5.

Returning now to GM 95, the freak in the litter, here is a checkpoint on basic solving, followed by the grid with the last boxline removal.

GM 95 basic traceGM 95 LMNext, I continue with the bv scan, and have some success with the XY-chain tracks. Look at the X-panel, and think about what to do about the cloud of 6-candidates.  That leads me in a very interesting direction that applies to cloud prone puzzles.

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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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