Compilare: main.cpp: In function 'void add(int)': main.cpp:24:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 24 | if(i == s.size()){ | ~~^~~~~~~~~~~ main.cpp: In function 'void del(int)': main.cpp:62:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 62 | if(i == s.size()){ | ~~^~~~~~~~~~~ main.cpp: In function 'void frequency(int)': main.cpp:98:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 98 | if(i == s.size()){ | ~~^~~~~~~~~~~ main.cpp: In function 'void get_prefix(int)': main.cpp:126:10: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 126 | if(i == s.size()){ | ~~^~~~~~~~~~~