How does the reserve function work in C++ std::vector?

Can you explain how the reserve function works in C++ std::vector?

Sure! The reserve function in std::vector is used to allocate memory for a specified number of elements, which can help improve performance by reducing the number of reallocations.

Why is it important to use reserve before adding elements?

Using reserve can prevent multiple reallocations as you add elements, which can be costly in terms of performance, especially for large vectors.

Can you show me a code example of using reserve?

Absolutely! Here's a simple example:

#include <vector>

int main() {
    std::vector<int> vec;
    vec.reserve(10); // Reserve space for 10 integers
    for (int i = 0; i < 10; ++i) {
        vec.push_back(i);
    }
}

What happens if I don't use reserve?

If you don't use reserve, the vector will automatically resize as you add elements, which may lead to multiple reallocations and can slow down your program.