What is the difference between using a struct with two fields and a pair?

Question

What is the difference regarding memory allocation and efficiency between using a struct with two fields and a pair?

Answer 1

std::pair comes with a number of constructors and operators.

A struct allow named fields (other than first and second) and is ready to be extended at any time.

Prefer a struct when you can. It may involve some overhead, but is definitely easier for maintenance.