The Number of Comparisons in QuickSort

Manuel Eberl 🌐

March 15, 2017

Abstract

We give a formal proof of the well-known results about the number of comparisons performed by two variants of QuickSort: first, the expected number of comparisons of randomised QuickSort (i. e. QuickSort with random pivot choice) is 2 (n+1) Hn - 4 n, which is asymptotically equivalent to 2 n ln n; second, the number of comparisons performed by the classic non-randomised QuickSort has the same distribution in the average case as the randomised one.

BSD License

Topics

Theories of Quick_Sort_Cost