Final answer:
The vector class in C++ automatically expands by allocating a larger block of memory to accommodate new elements, using dynamic array resizing. This ensures that the vector can grow as needed, although reallocations may involve a computational cost which can be mitigated with the reserve function.
Step-by-step explanation:
When a student asks if the vector class automatically expands, they are inquiring about the behavior of the vector class in the context of computer programming, specifically within C++ standard library templates.
The vector class in C++ does automatically expand as new elements are added to it. When the vector's current storage is insufficient to accommodate new elements, it allocates a larger block of memory, typically with extra space to accommodate future growth and minimizes the need for subsequent re-allocations. This process is called dynamic array resizing or automatic resizing.
The reallocation of memory generally involves copying of existing elements to the new memory block, which can be computationally expensive. However, smart memory allocation strategies employed by the vector class mitigate the performance impact of growth. To further manage performance and reduce the number of reallocations, the reserve function can be used to pre-allocate memory for a certain number of elements if the number of elements to be stored is known beforehand.