NAME
radixsort,
sradixsort —
radix sort
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <limits.h>
#include <stdlib.h>
int
radixsort(
const
u_char **base,
int
nmemb,
u_char *table,
u_int endbyte);
int
sradixsort(
const
u_char **base,
int
nmemb,
u_char *table,
u_int 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
Upon successful completion 0 is returned. Otherwise, -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.
Additionally, the
sradixsort() function may fail and set
errno for any of the errors specified for the library
routine
malloc(3).
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.