std::deque<T,Allocator>::shrink_to_fit (3) - Linux Man Pages
void shrink_to_fit(); (since C++11)
Requests the removal of unused capacity.
It is a non-binding request to reduce the memory usage without changing the size of the sequence. It depends on the implementation whether the request is fulfilled.
All iterators and references are invalidated. Past-the-end iterator is also invalidated.
T must meet the requirements of MoveInsertable.
At most linear in the size of the container.
If an exception is thrown other than by T's move constructor, there are no effects.
// Run this code
size (public member function)