carbone

#include <iostream>
#include <string>

int main() {
       std::string str{"first word and last"};
       int ind = str.find(' ');
       std::string first_word = str.substr(0, ind);
       int ind2 = str.rfind(' ');
       std::string last_word = str.substr(ind2+1);
       str.replace(0, ind, last_word);
       str.replace(ind2, last_word.length(), first_word);
       std::cout << str;
       return 0;
}