create linked list 10 -> 12 -> 8 -> 4 -> 6
push ( & head , 6 ) ; push ( & head , 4 ) ; push ( & head , 8 ) ; push ( & head , 12 ) ; push ( & head , 10 ) ; cout << " Linked ▁ list ▁ before ▁ sorting : n " ; printList ( head ) ;