Compilare: main.cpp: In function 'void find_pref_subs(std::__cxx11::string, int (&)[751000])': main.cpp:12:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < s.length(); ++i) { ~~^~~~~~~~~~~~ main.cpp:18:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (R < s.length() && s[R] == s[R - i]) ~~^~~~~~~~~~~~