What is the purpose of the reserve function in C++?

The reserve function is used to allocate space in a container ahead of time, allowing elements to be added later without the need to reallocate memory. This preemptive allocation helps avoid the performance overhead of multiple memory reallocations. Using the reserve function when adding a large number of elements to a container can improve program performance. The reserve function is only effective for resizable containers such as vector, deque, string, etc.