Compilare: main.cpp: In function 'int main()': main.cpp:24:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 24 | for (j = 0; j < s.size(); j++) | ~~^~~~~~~~~~ main.cpp:52:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 52 | for (i = 0; i < v[x].size(); i++) | ~~^~~~~~~~~~~~~