Compilare: main.cpp: In function 'void add(std::__cxx11::string, int)': main.cpp:23:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (it < S.size() && node->v[S[it] - 'a'] != NULL){ ~~~^~~~~~~~~~ main.cpp:27:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (it < S.size()){ ~~~^~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:67:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < failed->v[i]->index.size(); ++j){ ~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp:78:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i < s.size(); ++i){ ~~^~~~~~~~~~ main.cpp:84:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < curr->index.size(); ++j){ ~~^~~~~~~~~~~~~~~~~~~~