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.
Happy 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.
I 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
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.
And the trial runs out of gas without contradiction! I might be stuck, but the 2-brigade arrives with good news:
Only 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.
With 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.