std::begin and std::end free functions were added to return begin and end iterators of a container generically. These functions also work with raw arrays which do not have begin and end member functions.

template <typename T>
int CountTwos(const T& container) {
  return std::count_if(std::begin(container), std::end(container), [](int item) {
    return item == 2;
  });
}

std::vector<int> vec = {2, 2, 43, 435, 4543, 534};
int arr[8] = {2, 43, 45, 435, 32, 32, 32, 32};
auto a = CountTwos(vec); // 2
auto b = CountTwos(arr);  // 1