How Can I Efficiently Sum the Elements of a C Vector?

Determining the Sum of Elements in a C Vector

In C , finding the sum of elements in a std::vector requires a loop or standard algorithm to iterate over and accumulate the values. The choice of method depends on the version of C used, and each approach offers its own advantages.

C 03

• Classic for loop: Using a traditional for loop to iterate through the elements and increment a running sum variable.

  int sum_of_elems = 0;
  for (auto it = vector.begin(); it != vector.end(); ++it)
    sum_of_elems += *it;

• accumulate algorithm: This algorithm provided by the header accumulates the sum of elements passed through an iterator range.

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

C 11 and Higher

• std::accumulate with auto-typing: The same std::accumulate algorithm can be used with a slight modification to automatically deduce the return type based on the vector's element type.

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

• std::for_each loop: This loop syntax applies a lambda function to each element of the vector, updating a sum variable within its scope.

  std::for_each(vector.begin(), vector.end(), [&](int n) { sum_of_elems += n; });

• Range-based for loop: This syntactic sugar for loops iterates over the elements directly without a separate iterator object.

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

C 17 and Later

• std::reduce algorithm: This algorithm combines the elements of a collection into a single result using a specific binary operator, in this case addition. It also automatically infers the result type.

  #include <numeric>
  auto result = std::reduce(v.begin(), v.end());

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