Compilare: user.cpp: In member function ‘trie* trie::update(int)’: user.cpp:21:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pos == s_to_update.size()) { ~~~~^~~~~~~~~~~~~~~~~~~~~ user.cpp: In member function ‘void aho_corasick::compute_ans(std::__cxx11::string)’: user.cpp:72:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < S.size(); ++i) { ~~^~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:94:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ahocorasick.in","r",stdin); ^ user.cpp:95:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ahocorasick.out","w",stdout); ^