The New Sudoku Players' Forum

[Karyobin]

To find a hidden single you only need to focus on a digit and crisscross what's on the grid. To find a naked single you need to look for all other 8 digits, so it takes longer.

The same thing happens with hidden and naked pairs. When solving without pencilmarks, hidden pairs are just easier to see.

Absolutely right. Personally however, I think only in terms of Single, Pair or higher when working without pencilmarks, on the principle that they can't be hidden if there's nothing in the way.

[tso]

Nick70's solution is perfect and blows my comments about relative difficulty out of the water. When reading the forum, I don't always take the time to print out the puzzles in question and solve them on paper -- in this case, I really should have.

[Lummox JR]

I know a number of people here have suggested that a puzzle with subsets is difficult to impossible without pencil marks, but I just don't get this. I've found naked singles do present a challenge, but they're findable. Subsets though aren't that hard, and hidden subsets tend to be easier in this case than naked subsets.

I often like to handle the puzzles at websudoku.com, on the Evil level. Their bar is pretty low, though; their evil puzzles need nothing more complex than subsets, except in one or two cases where X-wing turned out to be helpful. There the solving is done entirely without pencilmarks, and subsets are actually easier to spot than you'd think.