Compilare: user.cpp: In function ‘std::string compute_pattern(const string&)’: user.cpp:15:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < w.size(); i++) { ^ user.cpp: In function ‘void solve(std::ifstream&, std::ofstream&, const std::unordered_set<std::basic_string<char> >&)’: user.cpp:53:8: warning: unused variable ‘c’ [-Wunused-variable] char c; ^