Compilare: main.cpp: In function 'void add(int)': main.cpp:25:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 25 | if(i == s.size()) | ~~^~~~~~~~~~~ main.cpp: In function 'void del(int)': main.cpp:59:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 59 | if(i == s.size()) | ~~^~~~~~~~~~~ main.cpp: In function 'void frequency(int)': main.cpp:93:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 93 | if(i == s.size()){ | ~~^~~~~~~~~~~ main.cpp: In function 'void get_prefix(int)': main.cpp:129:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 129 | if(i == s.size()) | ~~^~~~~~~~~~~