Compilare: user.cpp: In function ‘bool check(std::string, std::string)’: user.cpp:28:9: warning: unused variable ‘r’ [-Wunused-variable] int r=0; ^ user.cpp: In function ‘int main()’: user.cpp:48:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<a.size(); j++){ ^ user.cpp:59:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<b.size(); j++){ ^ user.cpp:79:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<u.size(); i++){ ^