An Untyped UR Rattles World’s Hardest 188

The review of World’s Hardest Sudoku continues with a quick dispatch of puzzle 188 by a unique rectangle and straightforward coloring. The UR fails its type category, but the examination uncovers an almost accidental chain interpreted after the fact as an AIC dirty rectangle.

Basic is quiet, with a good bypass start, and moderate line marking.





After confirming that the possible UR is not Type 3 or 4, the search is continued on possibility that a candidate eliminating one extra digit can also eliminate another. It happens here to 5r1c1 in a Rube Goldberg chain of events you can mark as an unusual AIC with a naked triple node. Can you draw up a for that?


My version is at the end of the post.

The next move is suggested by many bv and line slinks in values 1 – 4. A coloring is based on the four connecting  slinks of the 4-panel. There is a quick wrap of green in row 3 and collapse is immediate.

World’s Hardest?  Hardly.




Next post in the review traces two more basic solutions. One ends in the bypass, the other, in line marking. The puzzles are 46 at  left, and 186 on the right, both rated 0.90.

This leaves Worlds Hardest 134, and advanced achiever, to finish the review.

There’s a new page in the Sysudoku Guide, on Death Blossoms. The new page is accessed from the side menu of the BV Scan page.

As for the expression of the UR elimination in AIC speak, here’s mine. In addition to regular grouping, we have to isolate the naked triple and treat it as a node on the chain.


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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