Compilare: main.cpp: In function 'int main()': main.cpp:17:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 17 | for (int i=0; i<s.length(); i++) | ~^~~~~~~~~~~ main.cpp:20:24: 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 (int j=i; j<s.length(); j++) | ~^~~~~~~~~~~ main.cpp:27:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 27 | for (int i=0; i<=s.length()/2; i++) | ~^~~~~~~~~~~~~~