This continues the review of Will Shortz’ Hard Sudoku v.1, with another documented basic finish. Starting the Guide? Accounting for each move in this series, then trying them beforehand, will make Sysudoku basic yours.
Beware 175 matches 165’s collapse point, but with slightly different triggers, a boxline and a naked pair.
The box/line interaction, or boxline, occurs when marking line r5. No 9 candidate appears in r5 outside the East box, so the true 9 is in r5. The other E9 hopefuls must clean out their desks, and leave the building.
The naked pair begins the collapse.
Next week, its Beware 185. The Hard Sudoku v.1 review ends with 195, then my plan is return to earlier reviews to update all review posts to Guide methods and drawing conventions, with weekly post reporting on changes. The earlier posts will remain accessible through Title and Find It pages, and the monthly archive pages. New collection reviews can be undertaken on reader request.
The first review update is half done. It is the KrazyDad Insane collection, beginning mid July 1013.
Systematic Sudoku 
I was wondering if you could recommend which Krazy Dad puzzles might be a comparable follow-up to these Will Shortz puzzles? Novice, intermediate or challenging?
I’m looking for some more experience in finding subsets, particularly hidden subsets. These seem to be my nemesis when I solve the puzzles in my daily paper, the Arizona Republic. I usually find them with line marking. Or if I back up a step and find an overlooked hidden single, then the puzzle collapses.
thanks,
-gerald.
Thanks for the new comment, Gerald. On your question, I would guess “challenging”. With Will Shortz Hard Sudoku v1, it becomes a challenge only if you attempt the Sysudoku bypass. It doesn’t get to advanced. I only have experience with the SuperTough and Insane KD collections, through the reviews. The Insane review update is underway and its up through v4 b6 n5.
In the Guide, my best spotting advice is the habit of checking as soon as the candidates are complete, such as after marking each line. Naked subsets are easier to spot, even when larger in size. The naked tells on the hidden. For hiddens, look for n values restricted to n cells, especially when completing a line or box. Although it isn’t generally needed, working the scratchhpad algorithm I give for enumerating ALS and subsets will certainly sharpen your subset spotting.