Constant-sized vector

The std::vector can always grow dynamically, but there are two ways you can allocate an initial size:

This allocates initial size and fills the elements with zeroes:

std::vector<int> v(10);
v.size(); //returns 10

This allocates an initial size but does not populate the array with zeroes:

std::vector<int> v;
v.reserve(10);
v.size(); //returns 0