This post features hidden and naked subsets in two Sudoku X-treme review puzzles. All occur in line markings. The first continues from the previous post.
The second follows soon thereafter in the closing the first column. Below is a trace of the collapse which follows.
The X-treme review puzzles also demonstrate their fair share of hidden subsets.
In X-treme165, the very first line marking, shown below, is a very obvious hidden single. There is only one location permitted for a 6. Of course the always complementary naked triple is no less obvious.
Two lines later in line marking X-treme 165, we encounter another subset situation. In r8, do we have a naked quad or a hidden single? The answer is, it’s both. Whichever you find easier to recognize.
The new clues 7r8c5 and 7r8c4 trigger the box/line eliminating 1r9c8, and shortly thereafter we have a surge of eliminations as 5r4c7’s naked triple generates two naked pairs. Here is the “before”. Want to mark it from there? Next post will show the “after” that sends X-treme 165 into collapse.
If you have it, dust off your copy of Peter Gordon’s Mensa Guide to Solving Sudoku. Very recently, the Mensa association was dropped, with the re-issue under a Sterling Publishing imprint PuzzleWright. We’ll be doing a detailed critique of Gordon’s instruction and examples, in two parts. The basic solving part continues this basic clinic. The advanced solving part – and a review of the puzzle collection by Frank Longo – both follow later, after the basic clinic is completed.
I’m hurrying the basic part of the Gordon review into the basic clinic to get to a related strategy for timed solving contests of basic level puzzles. The next Akron, Ohio Sudoku tournament is coming up.
Wish me luck Saturday. I’m running the Akron marathon.