Use push ( ) to construct linked list
push ( & head , 1 ) ; push ( & head , 2 ) ; push ( & head , 1 ) ; push ( & head , 12 ) ; push ( & head , 1 ) ; push ( & head , 18 ) ; push ( & head , 47 ) ; push ( & head , 16 ) ; push ( & head , 12 ) ; push ( & head , 14 ) ;