Konverziu v C++ spravíš pomocou stringstreamu:
std::stringstream ss;
for (int i = 0; i < 200; ++i) {
ss.seekp(0);
ss << i;
std::cout << ss.str() << std::endl;
}for (int i = 0; i < 200; ++i) {
std::cout << boost::lexical_cast<std::string>(i) << std::endl;
}