Compilare: main.cpp: In function 'bool make_freq()': main.cpp:16:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 16 | for(int i = 0; i < s.size(); i++) { | ~~^~~~~~~~~~ main.cpp:18:28: warning: comparison of integer expressions of different signedness: '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'} and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 18 | if(f[s[i]] > s.size() / 2) main.cpp: In function 'std::string solve()': main.cpp:28:26: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 28 | for(int i = 0; i < s.size(); i++) { | ~~^~~~~~~~~~