Compilare: main.cpp: In member function 'void Trie::insert(std::__cxx11::string&)': main.cpp:30:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length (); i++) { ~~^~~~~~~~~~~~~ main.cpp: In member function 'int Trie::find(std::__cxx11::string&)': main.cpp:41:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length (); i++) { ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:55:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("sabin.in", "r", stdin); ^ main.cpp:56:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("sabin.out", "w", stdout); ^