Compilare: user.cpp: In function ‘void make_graph(int, int)’: user.cpp:81:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < L[a1].size(); i ++) ^ user.cpp: In function ‘int dijkstra(std::pair<int, int>)’: user.cpp:126:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < L[st.second].size(); i ++) ^