Is it more efficient to copy a vector by reserving and copying, or by creating and swapping? [duplicate]

Answer 1

This is another valid way to make a copy of a vector, just use its constructor:

std::vector newvector(oldvector);

This is even simpler than using std::copy to walk the entire vector from start to finish to std::back_insert them into the new vector.

That being said, your .swap() one is not a copy, instead it swaps the two vectors. You would modify the original to not contain anything anymore! Which is not a copy.