Compilare: user.cpp: In member function ‘void Trie::add(std::string)’: user.cpp:92:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length(); i++) { ^ user.cpp:96:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == s.length() - 1) ^ user.cpp:102:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == s.length() - 1) ^ user.cpp: In member function ‘int Trie::get(std::string)’: user.cpp:110:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length(); i++) { ^ user.cpp:114:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == s.length() - 1) ^ user.cpp: In member function ‘int Trie::lpm(std::string)’: user.cpp:126:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < s.length(); i++) { ^