For what it's worth I learned that explicitly in a data structures & algorithms class. I've seen it come up in a bunch of other introductory material, so it seems like a relatively standard part of "the curriculum." I think somebody might have a chance of coming up with this shortcut on their own, if, for example, they wanted to compute the Nth Fibonacci number efficiently (using matrix exponentiation -- the bignum arithmetic makes it O(n^2) if you just do n multiplications) or if they wanted to compute a polynomial more efficiently by memoizing the values x^(2^n), or if you kidnapped them and threatened to kill their family if they couldn't figure out how to compute x^n using O(log_2(n)) multiplications...
The difficult thing about that shortcut isn't that you couldn't come up with it, it's that you wouldn't think to try coming up with it unless you are in a particularly painful situation.
I don't view this exponentiation speedup stuff as math-specific, it's something you can come across when efficiently updating string checksums under random access modifications and concatenations, or when solving some graph problem where you exponentiate an adjacency matrix.
I'm glad your algorithm class covered this. Mine did not. It surely covered some other obscure material that you don't know. You are missing the point. If we had a standard CS curriculum, you can fault people for missing out on stuff they should know. I think part of the problem is people is that CS is too big of a discipline at this point. A systems person couldn't pass a graphics person's interview, etc.
The difficult thing about that shortcut isn't that you couldn't come up with it, it's that you wouldn't think to try coming up with it unless you are in a particularly painful situation.
I don't view this exponentiation speedup stuff as math-specific, it's something you can come across when efficiently updating string checksums under random access modifications and concatenations, or when solving some graph problem where you exponentiate an adjacency matrix.