Compilare: main.cpp: In member function 'bool cmp::operator()(pi, pi)': main.cpp:42:31: warning: statement has no effect [-Wunused-value] pd[a.first][a.second] > pd[b.first][b.second]; ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~ main.cpp:43:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^