dailysudoku.com

[richfa]

Not hard at all ... should be classified as easy.

[RobertRattley]

I did not find it easy. After placing a 9, two 5s, four 6s, three 4s, an 8, two 2s and a 7 I needed a triple 189 in the top left box to find two sole candidates in that box.

[richfa]

Hmmm, I placed, in the following order, 7, 2, 4, 6, 5, 8, 5, 6, 4, 6, 2, 9. This left me with 1-8, 1-8-9, 1-8-9 in the upper left box, which allowed me to place the 7, and clean up the rest of the puzzle of singles or hidden singles!

[RobertRattley]

Yes. Dealing with "1-8, 1-8-9, 1-8-9 in the upper left box" is what I meant by a "triple". It is a "hard" step.

Well, this is my understanding of the classifications on this site.

[rmireland]

When you get to the point where the naked 189 triple is there, the seven can also be exposed as a sole candidate ( in either box 1 or c2 ) by the 36 hidden pair in r12c2.
I don't know if hidden pairs are "harder" than naked triples in the Sudoku sense. Usually I prefer naked things to hidden things, but that's just me.
For some real excitement, you can also expose the seven sole candidate with the naked quad, 2459, in r4689c2.

[richfa]

I wouldn't classify one triple in the entire puzzle as making it hard. Maybe medium then? There are many discussions on how to rate the difficulty of a Sudoku puzzle and I believe that this would fall in to the medium class, at most.

@rmireland I agree that a naked anything is easier to spot than hidden things!