How do you do this?

[101dalmatians]

2010 A Invitational:

Given an array of N distinct elements in random order, what is the Big O of the traditional implementation of the quicksort
algorithm?

A. O(NlogN) B. O(N2) C. O(N2logN) D. O(N3/2) E. O(N3)

[le cool cat]

This is a memorization problem. it's O(nLogn). http://en.wikipedia.org/wiki/quicksort