Coloring Wrings Out World’s Hardest 102

World’s 102 starts without ‘1’ givens and with two 3-fill lines. It winds up in a coloring trap expansion into a wrap.

Basic makes progress in all three phases.








Making a hasty bv scan and skipping the XYZ analysis, I go to the bv map and sketch out an extensive railway, for a easy ANL, resulting in a second naked triple.

Why not?





The next greedy move on the 21 bv banquet table is coloring. Starting with  these two traps, a trapping expansion removes 6r6c4, 6r4c5, 6r9c5,and 4r9c1.





Collapse is immediate as SW1 wraps green. Blue mops up.










Next is World’s Hardest 188. When you get to advanced, look for an unconventional unique rectangle.



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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