Quicksort

Quicksort is a sorting algorithm developed by Tony Hoare that, on average, makes O(n log n) comparisons to sort n items. It is also known as partition-exchange sort. In the worst case, it makes O(n2) comparisons, though this behavior is rare. Quicksort is often faster in practice than other O(n log n) algorithms. Additionally, quicksort's sequential and localized memory references work well with a cache. Quicksort can be implemented with an in-place partitioning algorithm, so the entire sort can be done with only O(log n) additional space.

Quicksort is a comparison sort and, in efficient implementations, is not a stable sort.