TimSort, backported from JDK7 sources (build openjdk-7-ea-src-b77-03_dec_2009).
Javadocs copied accordingly as well.
A stable, adaptive, iterative mergesort that requires far fewer than
n lg(n) comparisons when running on partially sorted arrays, while
offering performance comparable to a traditional mergesort when run
on random arrays. Like all proper mergesorts, this sort is stable and
runs O(n log n) time (worst case). In the worst case, this sort requires
temporary storage space for n/2 object references; in the best case,
it requires only a small constant amount of space.
This implementation was adapted from Tim Peters's list sort for
Python, which is described in detail here:
Tim's C code may be found here:
The underlying techniques are described in this paper (and may have
even earlier origins):
"Optimistic Sorting and Information Theoretic Complexity"
SODA (Fourth Annual ACM-SIAM Symposium on Discrete Algorithms),
pp 467-474, Austin, Texas, 25-27 January 1993.
While the API to this class consists solely of static methods, it is
(privately) instantiable; a TimSort instance holds the state of an ongoing
sort, assuming the input array is large enough to warrant the full-blown
TimSort. Small arrays are sorted in place, using a binary insertion sort.