NEED HELP ASAP!!!

Assume that there is a doubly linked list which is sorted and the size (number of elements in the list) of the doubly linked list is given. You are asked to implement a "Contains (X)" method which returns true if given element X is there in the doubly linked list. If X is not present in the doubly linked list, then this method returns false. Try to implement the method in O(log n) complexity. (Partial credit will be given for method in O(n) complexity)