Compilare: user.cpp: In function ‘void topological_sort(int)’: user.cpp:38:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < g[node].size(); ++i) ^ user.cpp: In function ‘void mark(int)’: user.cpp:56:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < rg[node].size(); ++i) ^ user.cpp: In function ‘void write()’: user.cpp:113:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < groups[i].size(); ++j) ^