mergesort — sort
size_t nmemb, size_t size,
int (*compar)(const void *, const void *));
function is a modified selection sort. The
mergesort() function is a modified merge sort with
exponential search intended for sorting data with pre-existing order.
function sorts an array of nmemb objects, the initial
member of which is pointed to by base. The size of
each object is specified by size. The
mergesort() function behaves similarly, but
that size be greater than “sizeof(void *) /
The contents of the array base are sorted in ascending order according to a comparison function pointed to by compar, which requires two arguments pointing to the objects being compared.
The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.
function is an implementation of J.W.J. William's
“heapsort” algorithm, a variant of selection sorting; in
particular, see D.E. Knuth's
takes O N lg N worst-case time. Its
qsort() is that it uses almost no
additional memory; while
qsort() does not allocate
memory, it is implemented using recursion.
requires additional memory of size nmemb *
size bytes; it should be used only when space is not
at a premium. The
mergesort() function is optimized
for data with pre-existing order; its worst case time is O N lg N; its best
case is O N.
mergesort() is faster than
heapsort(). Memory availability and pre-existing
order in the data can make this untrue.
mergesort() functions return the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
mergesort() functions succeed unless:
Williams, J.W.J, Heapsort, Communications of the ACM, 7:1, pp. 347-348, 1964.
Knuth, D.E., Sorting and Searching, The Art of Computer Programming, Vol. 3, pp. 114-123, 145-149, 1968.
McIlroy, P.M., Optimistic Sorting and Information Theoretic Complexity, Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, January 1992.
Bentley, J.L. and McIlroy, M.D., Engineering a Sort Function, Software--Practice and Experience, Vol. 23(11), pp. 1249-1265, November 1993.
|September 30, 2003||Debian|