Compilare: user.cpp: In function ‘int brute_force(const string&)’: user.cpp:57:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < str.size(); ++i){ ^ user.cpp:58:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i+3, thlen = 1; j <= str.size(); j += 3, ++thlen){ ^ user.cpp: In instantiation of ‘void z_alg(int, It1, It2) [with It1 = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >; It2 = __gnu_cxx::__normal_iterator<int*, std::vector<int> >]’: user.cpp:44:28: required from ‘int count_here(int, It) [with It = __gnu_cxx::__normal_iterator<const char*, std::basic_string<char> >]’ user.cpp:52:44: required from here user.cpp:17:24: warning: unused variable ‘st’ [-Wunused-variable] for(int i = 1, st = 0; i < n; ++i){ ^