How can I find a number which occurs an odd number of times in a SORTED array in O(n) time?

Question

I have a question and I tried to think over it again and again... but got nothing so posting the question here. Maybe I could get some view-point of others, to try and make it w

Answer 1

Take the middle element e. Use binary search to find the first and last occurrence. O(log(n)) If it is odd return e. Otherwise, recurse onto the side that has an odd number of elements [....]eeee[....]

Runtime will be log(n) + log(n/2) + log(n/4).... = O(log(n)^2).