We all know that Quicksort is one of the fastest algorithms for sorting. It's not often, however, that we get a chance to see exactly how fast Quicksort really is. The following Applets chart the progress of several common sorting algorithms while sorting an array of data using in-place algorithms. This means that the algorithms do not allocate additional storage to hold temporary results: they sort the data in place. (This is inspired by the algorithm animation work at Brown University and the video Sorting out Sorting By Ronald Baecker from the University of Toronto (circa 1970!).)
Some of these sorts are very stupid or very slow and should not be used in code. The use of Bubblesort is deprecated.
In-Place Mergesort is yet another abomination. Mergesort is supposed to run in O(n log n), but the implementation here runs in O(n * n). This is because a temporary scratch array is not used. As with most of the examples here, In-Place Mergesort sorts the elements in the array without using additional storage (other than the stack used for the recursive calls, and temporary variables). Jack Snoeyink has provided me with a the Double Storage mergesort algorithm sort implementation that uses a scratch array.
Click on each applet to see the algorithm run. Click on the name of the algorithm to see the source.The bibliography appearing at the end of this article lists 37 sorting algorithms and 100 books and papers on sorting published in the last 20 years. The ideas presented here have been abstracted from this body of work, and the best algorithms known are given as examples. As the algorithms are explained, references to related algorithms and mathematical or experimental analyses are given. Suggestions are then made for choosing the algorithm best suited to a given situation.
Disclaimer: If you use this page as part of your teaching, please let me
know. I tend to refer students who ask too many questions back to their
instructor. Requests for translations of the Java sources to other
programming languages will be denied. This page was created in a fit of
"thesis avoidance" in the summer of 1996.
James Gosling