On Mon, Dec 15, 2008 at 11:05 AM, <prueba...@latinmail.com> wrote: >> Non-comparison sorts are a useful technique, but it's changing the >> problem, and they are only useful in very limited circumstances. There's >> a good reason that most sort routines are based on O(n*log n) comparison >> sorts instead of O(n) bucket sorts or radix sorts. >> > This is an assumption that I never quite understood. What most people > want is to have sorted data, they don't care if I used a sorting or > non-sorting comparison to do it. I think it is just that in most cases > n is not very big anyway and comparison sorts make it easier on the > programmer to create arbitrary types that are sortable.
And if n is small and sparse (ie, k > n) , O(k*n) for radix sort could be worse than O(n^2). You could also ask why people make such a big deal about quicksort over mergesort, since mergesort has a guaranteed O(n log n) time whereas quicksort can be O(n^2) on pathological cases. I think I remember learning in my algorithms class that for small sorts (n < ~40) , bubblesort can actually be the fastest (or close to the fastest) in terms of wall-clock time because it has a relatively small constant factor in its O(n^2) complexity. -- http://mail.python.org/mailman/listinfo/python-list
