Answers for "number of elements in vector c++"

c++ vector size

#include <vector>

int main() {
  std::vector<int> myVector = { 666, 1337, 420 };
  
  size_t size = myVector.size(); // 3
  
  myVector.push_back(399); // Add 399 to the end of the vector
  
  size = myVector.size(); // 4
}

c++ count vector elements

// 1.
for(std::vector<int>::iterator it = vector.begin(); it != vector.end(); ++it)
    sum_of_elems += *it;

// 2.
// #include <numeric>
sum_of_elems = std::accumulate(vector.begin(), vector.end(), 0);

// C++11 and higher
// 3.
// #include <numeric>
sum_of_elems = std::accumulate(vector.begin(), vector.end(),
                               decltype(vector)::value_type(0));

// 4.
for (auto& n : vector)
    sum_of_elems += n;