C++ sample of using a vector with auto for an iterator

vector_sample.cpp

#include <iostream>                                                             
#include <vector>

int main() {
  std::vector<int> v {1, 2, 3}; 
  for (auto& i : v) {
    std::cout << i;
  }
  std::cout << std::endl;
  return 0;
}