Compilare: main.cpp: In function 'std::string encode(std::string)': main.cpp:10:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 10 | for(int i=0; i<s.size(); i++) | ~^~~~~~~~~ main.cpp: In function 'std::string decode(std::string)': main.cpp:20:19: 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 i=0; i<s.size(); i++) | ~^~~~~~~~~ main.cpp: In function 'int main()': main.cpp:36:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 36 | for(int i=0; i<a.size(); i++) | ~^~~~~~~~~