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c++stdvectorswap

Performance of std::vector::swap vs std::vector::operator=

Given two vectors of equal length:

std::vector<Type> vec1;
std::vector<Type> vec2;

If the contents of vec2 need to be replaced with the contents of vec1, is it more efficient to use

vec2.swap(vec1);

or

vec2 = vec1;

assuming that vec1 will remain in memory but its contents after the operation don't matter? Also, is there a more efficient method that I haven't considered?

Solution

  • swap will be more efficient since no copy is made. = will create a copy of vec1 in vec2, keeping the original intact.

    If you check the documentation, you'll see that swap is constant while = is linear.