A Surprising Dave Green Sunday 5-Star

My Sunday morning ritual Sudoku, the Dave Green 5-star of September 3, 2017,  sent me upstairs for PowerPoint support. This one breaks tradition by surviving Sysudoku basic, and with a heavy line marking. After no other advanced progress,  a four cluster coloring proves 10 solutions.  You get another demonstration of coloring as a humanly practical way to deal with multiple solutions.

The difficult line marking, and just getting through basic, were signs that this was not my typical Sunday treat.

Fortunately, I got it transcribed to the template before the newsprint version became unreadable. 

Nothing worked for me until this very indecisive coloring trap and possible bridge prompted more clusters.

The red vs. green conflict in r7 means blue or orange or both are true. But no 8’s see blue or orange.




I added pink/tan  and aqua/yellow clusters. No further conflicts, so I start a red trial. In the trial, yellow would generate a two- solution rectangle.

Discarding yellow, evidence of multiple solution appears as aqua and tan generate a four line extended rectangle in the East tower, while aqua and pink bring a third solution.

The multiple solution justifies going back to yellow in the red trial to pick up the rectangle multiple.  Blue, red, and tan accompany yellow, and an independent extended rectangle emerges, for four more solutions.


Finally, aqua/orange/blue trials add two solutions,  and aqua/orange/green provide the newspaper’s, the double sized .

Ouch! The unintended multiple solutions explain the sudden jump in difficulty from basic to extreme . The basic level record remains intact. Although BJ readers may question that with the 9/24/17 5-star I sat down to yesterday. It seems to require a one-term Sue de Coq, but one that could have been spotted in line marking. Dave, run the solver to the end. I don’t expect any more naughty 5-stars like this one, disturbing the Sunday morning peace.

Next week, I’ll post the less extreme ending of Manuel Castillo’s Only Extreme 3 that Gordon Fick sent me, and we’ll get on with the Only Extreme review.




About Sudent

I'm John Welch, a retired engineering professor, father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. Sudoku analysis and illustration is a great hobby and a healthy mental challenge.
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