I'm not too sure, but I think these builtins are internally written in C, making them automatically blazing fast. Calling the solution "horribly inefficient" is really dramatic. On the grand scheme of things, this is still an O(n) solution. It is also incredibly readable. I have run some cursory benchmarks and the "inefficient" method gobsmacks yours for all list lengths I've tried (we're talking around more than 3x faster than yours). Take this with a grain of salt since they're informal tests, but it should hopefully make you reconsider making hasty performance comments in the future. I'll attach it spoilered below.

No. If you parse the array twice it's still O(N) (O(2N) == O(N)). O(N^2) would be the case of a nested loop.

Your reply is non-sensical...I'm not sure where language comes into play here.

This solution runs in O(N^2) because it requires iterating through the array twice before returning.

With a two pointer solution, you traverse the array once, in O(N), which is more efficient.

if you want efficiency, you should use other programming languages...

Python is not famous for its efficiency...

This solution is terribly inefficient.

you absolutely should do this in an interview, it shows understanding of the language methods. But come on, nobody is going to ask this in an interview anyway.

unless its coding in python...? please state why. This is more understandable for other, especially more lower-level / typed languages... but why?

Don't do this during an interview.

Don't do this in an interview