Fastest way to search for an element in unsorted array

Question

I just bumped on to this question today and was trying for a solution that is better than O(N) but could not come up with one.

Searched through SO but couldn\'t find

Answer 1

It is possible to make your program run faster than O(n).

You start off by sorting the array using the merge sort algorithm, then you use binary search to find the element. Both algoro have a running time of O(log_2(n)). Adding these two complexities together, you get 2*log_2(n), which is O(log_2(n)) with the witness C = 2.