Dan Upton wrote:
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.
Python's current list.sort uses mergesort because it better exploits existing structure in a list.
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.
It uses binary insert sort for n < 64 (chosen empirically) . That also does O(n logn) comparisons and is only O(n**2) for data movement, which a decent C compiler translates into fast block-move assembly instructions.
tjr -- http://mail.python.org/mailman/listinfo/python-list
