how to calculate sum of a vector in c++ stl code example

Example 1: sum of vector c++

accumulate(a.begin(), a.end(), 0);

Example 2: sum elements in vector c++

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

Example 3: C++ sum a vector of digits

// Sum digits in vector
int digit_sum(vector<int> num) {
    int sum = 0;
    for (auto x : num) sum += x;
    return sum;
}