Compilare: user.cpp: In function ‘void topo(int)’: user.cpp:18:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i< l[nod].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:34:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < l[x].size() && ok; j++) ^