You can use a randomized selection algorithm to find the median in linear time, and if you use the median as a pivot you will never get worst case n^2 behavior.

You can use a randomized selection algorithm to find the median in linear time, and if you use the median as a pivot you will never get worst case n^2 behavior. This is not used in practice because the probability of getting worst case behavior is extremely slim if you do some clever, and cheap, tricks.