What is most challenging about learning and understanding Big O notation?

Once it clicks, Big O is easy to understand.

Did you (or do you) find Big O notation challenging to learn?

If so, why?

If not, why? When and how did it click?

Comments

[Curtis Fenner]

The biggest difficulty for me was keeping all of the different variants straight: o and O and Theta and omega.

That, and some of the equivalences aren't intuitive. The fact that some pairs of (increasing!) sequences aren't big-O of each other is also pretty mind bending.

It clicked after practicing the definition and learning lots of helpful rules that let you skip the actual definition (testing limit of ratio, polynomials, etc...)