[virgi1]

This. I can't believe nobody else pointed out that it's not n-squared. (but, lots of people pointed out that complexity is really about reasoning not about memorisation - and you have to be good at reasoning in order to be a good programmer).

And this is not an "esoteric question" - you should really have a good grasp on complexity in order to understand the limitations of your system, and when you can use certain algorithms/data structures, and when you can't.

See this write-up: http://www.infoarena.ro/blog/numbers-everyone-should-know - but don't memorize the numbers, that would be pointless - the idea is to get a feel of why complexity is important. (you'll notice for instance that between O(n!) and O(n^2) there is a 2-3 orders of magnitude difference in the acceptable input data size... so your confusion between factorial and n-squared is actually quite big)