how to iterate over the vecotr code example

Example 1: c++ iterate through vectgor

std::vector<int> vec_of_ints(100);
for (int i = 0; i < vec_of_ints.size(); i++){
 	std::cout << vec_of_ints.at(i) << " "; 
}
std::cout << std::endl;

Example 2: c++ looping through a vector

for(std::vector<T>::size_type i = 0; i != v.size(); i++) {
    v[i].doSomething();
}