Compilare: main.cpp: In function 'int main()': main.cpp:20:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | for(i=0; i<=s.size(); i++) | ~^~~~~~~~~~ main.cpp:22:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 22 | while(i<s.size() && check(s[i])) | ~^~~~~~~~~