Compilare: main.cpp: In function 'int main()': main.cpp:50:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 50 | for (int i = 0; i < s.size(); i++) | ~~^~~~~~~~~~ main.cpp:62:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<elem>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 62 | for (int j = 0; j < v[i].size(); j++) | ~~^~~~~~~~~~~~~