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Jens Axel Søgaard wrote:
* Four varieties of algorithms were provided (quick, heap, insert, merge) even though quick, heap, and insert sorts have no significant advantage over merge-sort. ... Second: What does "no significant advantage" mean? I were of the impression, that the "hidden constants" of O(n log (n)) of vector-quick-sort were smaller than that of vector-merge-sort.
My impression is that is non-trivially faster when you're sorting an array of integers, with no indirection through a "compare" function. In practice, one (almost) never sorts an array of integers (one sorts an array of records/objects - which may have integer fields), and one usually indirects though a compare function. That changes the "constant factors" significantly. It is illustrative that java.util.Arrays uses a "tuned quicksort" for sorting arrays of "primitive" (unboxed) numbers, but a "modified mergesort" to sort Object arrays. > Also: Is merge-sort the fastest algorithm, if the elements are "almost > sorted"? From the Java documentation: This [modified merge-sort] algorithm offers guaranteed n*log(n) performance, and can approach linear performance on nearly sorted lists. -- --Per Bothner email@example.com http://per.bothner.com/