Compilare: user.cpp: In function ‘void insert(std::__cxx11::string, int)’: user.cpp:29:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<w.length(); ++i) { ~^~~~~~~~~~~ user.cpp: In function ‘void propagate_counts(trie*)’: user.cpp:58:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<bfs_order.size(); ++i) ~^~~~~~~~~~~~~~~~~ user.cpp:66:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0; j<aux->words.size(); ++j) ~^~~~~~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:88:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.length(); ++i) { ~^~~~~~~~~~~