# [racket] Looking for feedback on code style

On 9/9/10 11:52 AM, Prabhakar Ragde wrote:
>* Selection can be done in O(n) time regardless of the value of k.
*
Ah, that's where I went wrong. I think I was confused by the Wikipedia
text on introselect, where k is a constant (unrelated the kth smallest
element).
>* The idea is to split the n elements into sets of 5, find the median of
*>* each set by an ad-hoc method, recursively find the median of the
*>* medians, and use that to partition the n elements as in the Quicksort
*>* method. That is guaranteed to remove about 3n/10 elements (every median
*>* smaller than the median of the medians, and two elements from each
*>* associated set). So you get a recurrence like
*>*
*>* T(n) = T(n/5) + T(7n/10) + O(n)
*>*
*>* which has a solution that is O(n). The constant is pretty high, though.
*
Thanks for the explanation.
David