Description : Reduces the capacity of the container to fit its size.
Example:
//create a vector of 5 elements
std::vector<int> myvec{10, 20, 30, 40, 50};
//adding a sixth element, vector's capacity will increase for future insertions
myvec.push_back(60);
//output the inital capacity
std::cout << "Initial capacity is: " << myvec.capacity();
//output the shrunk capacity
myvec.shrink_to_fit();
std::cout << "Shrunk capacity is: " << myvec.capacity();