How to get a pointer from a class c ++ vector

From c ++ 11 you can use the data function. It returns the address of the array used to store the vector elements. Note that if the vector has no elements, data() may or may not return nullptr

#include <iostream>
#include <vector>

int main() {
  std::vector<int> cheio{1, 2, 3};
  std::vector<int> vazio;
  cheio.clear();
  std::cout << std::boolalpha << "vazio.data() == nullptr? "
            << (vazio.data() == nullptr) << "\n"
            << "cheio.data() == nullptr? " 
            << (cheio.data() == nullptr) << "\n";
}

vazio.data() == nullptr? true
cheio.data() == nullptr? false