Compilare: user.cpp: In member function ‘void Trie::add(int)’: user.cpp:27:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(pos==s.size()) return; ^ user.cpp: In function ‘int main()’: user.cpp:54:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<s.size(); ++j) ^ user.cpp:63:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<s.size(); ++j) ^