Compilare: main.cpp: In member function 'void Trie::insert(std::__cxx11::string)': main.cpp:42:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length(); i++) { ~~^~~~~~~~~~~~ main.cpp: In member function 'bool Trie::_remove(std::__cxx11::string, int, TrieNode*)': main.cpp:57:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == s.length()) { ~~^~~~~~~~~~~~~ main.cpp: In member function 'int Trie::count(std::__cxx11::string)': main.cpp:73:27: 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::longest_prefix(std::__cxx11::string)': main.cpp:85:27: 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:102:12: warning: unused variable 'i' [-Wunused-variable] int q, i = 1; ^