Compilare: user.cpp: In member function ‘bool ar::operator<=(ar)’: user.cpp:15:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(val == -1) ^ user.cpp:17:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(b.val == -1) ^ user.cpp: In member function ‘bool ar::operator=(ar)’: user.cpp:25:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘void mark(int)’: user.cpp:35:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(arb[nod].val == -1) ^