things_that_exist.cpp

#include <cstdlib>
#include <string>
#include <numeric>
#include <execution>

// enable modern c++ if you're a cool enterprise person
#if MODERN_CPP

bool is_word_beginning(char l, char r) { return std::isspace(l) && !std::isspace(r); }
std::size_t word_count(std::string_view s) {
    if (s.empty()) return 0;
    return std::transform_reduce(std::execution::par_unseq,
        s.begin(), s.end() - 1, s.begin() + 1,
        std::size_t(!std::isspace(s.front()) ? 1 : 0),
        std::plus(),
        is_word_beginning
    );
}

int main() {
  std::string_view frost = "Whose woods these are I think I know.\n"
                           "His house is in the village though;  \n"
                           "He will not see me stopping here     \n"
                           "To watch his woods fill up with snow.\n";
  return word_count(frost);
}

#else

size_t word_count(const char* s) {
    size_t count = 0;
    for (; *s; s++) {
        count += isspace(s[0]) && !isspace(s[1]);
    }
    return count;
}

int main() {
  const char* frost =      "Whose woods these are I think I know.\n"
                           "His house is in the village though;  \n"
                           "He will not see me stopping here     \n"
                           "To watch his woods fill up with snow.\n";
  return word_count(frost);
}

#endif