An interesting side project of this would be describing how the difference between O(2^n) and O(3^n) or knowing what the heap operations are have been needed in your job.
And, since I'm asking already, I'd also like to know why you needed to know the information "on-the-fly" and couldn't have gotten there almost as easily with a quick refresher.
For example, I don't remember all the heap operations by heart but, if I needed to select a data structure for a critical task, I would go fetch Cormen and Skiena (the books, not the people) and get a quick refresher.
And, since I'm asking already, I'd also like to know why you needed to know the information "on-the-fly" and couldn't have gotten there almost as easily with a quick refresher.
For example, I don't remember all the heap operations by heart but, if I needed to select a data structure for a critical task, I would go fetch Cormen and Skiena (the books, not the people) and get a quick refresher.