NAME
radixsort, sradixsort — radix sortLIBRARY
library “libbsd”SYNOPSIS
#include <limits.h>#include <stdlib.h> (See libbsd(7) for include usage.)
int
radixsort(const unsigned char **base, int nmemb, const unsigned char *table, unsigned endbyte); int
sradixsort(const unsigned char **base, int nmemb, const unsigned char *table, unsigned endbyte);
DESCRIPTION
The radixsort() and sradixsort() functions are implementations of radix sort. These functions sort an nmemb element array of pointers to byte strings, with the initial member of which is referenced by base. The byte strings may contain any values. End of strings is denoted by character which has same weight as user specified value endbyte. endbyte has to be between 0 and 255. Applications may specify a sort order by providing the table argument. If non-NULL
,
table must reference an array of
UCHAR_MAX
+ 1 bytes which contains the sort
weight of each possible byte value. The end-of-string byte must have a sort
weight of 0 or 255 (for sorting in reverse order). More than one byte may have
the same sort weight. The table argument is
useful for applications which wish to sort different characters equally, for
example, providing a table with the same weights for A-Z as for a-z will
result in a case-insensitive sort. If table
is NULL, the contents of the array are sorted in ascending order according to
the ASCII order of the byte strings they reference and
endbyte has a sorting weight of 0.
The sradixsort() function is stable, that is, if
two elements compare as equal, their order in the sorted array is unchanged.
The sradixsort() function uses additional memory
sufficient to hold nmemb pointers.
The radixsort() function is not stable, but uses no
additional memory.
These functions are variants of most-significant-byte radix sorting; in
particular, see D.E. Knuth's
Algorithm R and section 5.2.5, exercise 10. They take
linear time relative to the number of bytes in the strings.
RETURN VALUES
The radixsort() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.ERRORS
- [
EINVAL
] - The value of the endbyte element of table is not 0 or 255.
SEE ALSO
sort(1), qsort(3) Knuth, D.E., Sorting and Searching, The Art of Computer Programming, Vol. 3, pp. 170-178, 1968. Paige, R., Three Partition Refinement Algorithms, SIAM J. Comput., No. 6, Vol. 16, 1987. McIlroy, P., Computing Systems, Engineering Radix Sort, Vol. 6:1, pp. 5-27, 1993.HISTORY
The radixsort() function first appeared in 4.4BSD.January 27, 1994 | Debian |