Compilare: main.cpp: In function 'bool ok(const string&, const string&)': main.cpp:53:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 53 | for (int i = 0 ; i < a.length() ; ++ i) | ~~^~~~~~~~~~~~ main.cpp:56:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 56 | if (idx == b.length()) return true; | ~~~~^~~~~~~~~~~~~