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

What will be the efficiency of algorithm that makes use of partition approach applied during quick-sort as follows?

1. Randomly select some value (let us call it v) in the list.

2. Partition the entire list into 2 parts. Left part contains all elements that are less than v. Right part contains all elements that are greater than v.

3. Repeat the steps 2, 3 until you determine whether the element exists or does not exist.

I am not sure about the complexity of above algorithm, but looks like it will be definitely less than the complexity of quick-sort algorithm: (n log n).