Quicksort, or partition-exchange sort, is a sorting algorithm that, on average, makes O(n log n) comparisons to sort n items. It was developed by Tony Hoare. Quicksort is faster in practice than other O(n log n) algorithms such as Bubble sort or Insertion Sort. 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 is not a stable sort.