Trick for releasing memory for C++ vector

For C++ vector, there's a huge problem that when you use either clear() or erase(), it won't release the memory for you. And there is "NO" direct way doing so. I searched on the internet and find one trick does that by using swap(). Here is the sample code by Tiyano (a student from Taiwan) explaining how it works.

#include

#include

using std::vector;

int main(void) {

vector A, B;

vector *C;

A.resize(1000);

printf("%d %d\n", A.size(), A.capacity());

A.clear();

printf("%d %d\n", A.size(), A.capacity());

A = B;

printf("%d %d\n", A.size(), A.capacity());

A.swap(B);

printf("%d %d\n", A.size(), A.capacity());

C = new vector;

C->resize(1000);

printf("%d %d\n", C->size(), C->capacity());

delete C;

C = new vector;

printf("%d %d\n", C->size(), C->capacity());

return 0;

}

The second method (new and delete) I'm not 100% sure it works, cuz in my case, the elements are pointers, so I adopt the first method which works.