Compilare: main.cpp: In member function 'virtual void Trie::add(std::__cxx11::string)': main.cpp:32:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < word.length(); i++) { ~~^~~~~~~~~~~~~~~ main.cpp: In member function 'virtual void Trie::remove(std::__cxx11::string)': main.cpp:50:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < word.length(); i++) { ~~^~~~~~~~~~~~~~~ main.cpp: In member function 'virtual int Trie::occurences(std::__cxx11::string)': main.cpp:79:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < word.length(); i++) { ~~^~~~~~~~~~~~~~~ main.cpp: In member function 'virtual int Trie::longestPrefixLength(std::__cxx11::string)': main.cpp:97:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < word.length(); i++) { ~~^~~~~~~~~~~~~~~ main.cpp: In function 'int main(int, const char**)': main.cpp:129:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("trie.in", "r", stdin); ^ main.cpp:130:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("trie.out", "w", stdout); ^