Question

The first solution is:

std::vector<int> *vec = new std::vector<int>;
assert(vec != NULL);
// ...
delete vec;

An alternative is:

std::vector<int> v;
//...
vec.clear();
vec.swap(std::vector<int>(vec));

The second solution’s a bit of a trick — what’s the "right" way to do it?

Update:

I’m aware that the destructor will be called once it’s off the stack, I was curious about other methods.

Answer 1

The simplest and most reliable way to deallocate a vector is to declare it on the stack and simply do nothing.

void Foo() {
  std::vector<int> v;
  ...
}

C++ guarantees that the destructor of v will be called when the method executes. The destructor of std::vector will ensure any memory it allocated is freed. As long as the T type of the vector<T> has proper C++ deallocation semantics all will be well.