Compilare: user.cpp: In function ‘int main()’: user.cpp:50:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<M && sol.size()<N-1;++i) ^ user.cpp:58:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<sol.size();++i)g<<Edges[sol[i]].x<<' '<<Edges[sol[i]].y<<'\n'; ^