Accessing elements
Having discussed the declaration and initialization of std::vector, our focus now shifts to accessing and manipulating the contained data. Multiple methods in C++ allow you to access vector elements with both speed and safety.
Random access
The subscript [] operator allows direct element access via indices, similar to arrays. In the following example, given a vector, the expression numbers[1] returns the value 20. However, using this operator doesn’t involve boundary checks. An index that is out of range, such as numbers[10], results in undefined behavior, leading to unpredictable outcomes.
This is shown in the following example:
#include <iostream>
#include <vector>
int main() {
  std::vector<int> numbers = {10, 20, 30, 40, 50};
  const auto secondElement = numbers[1];
  std::cout << "The second element is: " << secondElement
        ...
