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36 .\" @(#)qsort.3 8.1 (Berkeley) 6/4/93
37 .\" $FreeBSD: src/lib/libc/stdlib/qsort.3,v 1.4.2.5 2001/12/14 18:33:58 ru Exp $
38 .\" $DragonFly: src/lib/libc/stdlib/qsort.3,v 1.2 2003/06/17 04:26:46 dillon Exp $
44 .Nm qsort , heapsort , mergesort
51 .Fn qsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
53 .Fn heapsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
55 .Fn mergesort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
59 function is a modified partition-exchange sort, or quicksort.
62 function is a modified selection sort.
65 function is a modified merge sort with exponential search
66 intended for sorting data with pre-existing order.
72 functions sort an array of
74 objects, the initial member of which is pointed to by
76 The size of each object is specified by
79 behaves similarly, but
84 .Dq "sizeof(void *) / 2" .
86 The contents of the array
88 are sorted in ascending order according to
89 a comparison function pointed to by
91 which requires two arguments pointing to the objects being
94 The comparison function must return an integer less than, equal to, or
95 greater than zero if the first argument is considered to be respectively
96 less than, equal to, or greater than the second.
104 stable, that is, if two members compare as equal, their order in
105 the sorted array is undefined.
112 function is an implementation of C.A.R. Hoare's ``quicksort'' algorithm,
113 a variant of partition-exchange sorting; in particular, see D.E. Knuth's
116 takes O N lg N average time.
117 This implementation uses median selection to avoid its
118 O N**2 worst-case behavior.
122 function is an implementation of J.W.J. William's ``heapsort'' algorithm,
123 a variant of selection sorting; in particular, see D.E. Knuth's Algorithm H.
125 takes O N lg N worst-case time.
130 is that it uses almost no additional memory; while
132 does not allocate memory, it is implemented using recursion.
136 requires additional memory of size
139 bytes; it should be used only when space is not at a premium.
141 is optimized for data with pre-existing order; its worst case
142 time is O N lg N; its best case is O N.
150 Memory availability and pre-existing order in the data can make this
158 .Rv -std heapsort mergesort
164 functions succeed unless:
169 argument is zero, or,
175 .Dq "sizeof(void *) / 2" .
180 were unable to allocate memory.
185 did not permit the comparison routine itself to call
187 This is no longer true.
195 .%J "The Computer Journal"
203 .%J "Communications of the ACM"
210 .%B "The Art of Computer Programming"
212 .%T "Sorting and Searching"
213 .%P pp. 114-123, 145-149
217 .%T "Optimistic Sorting and Information Theoretic Complexity"
218 .%J "Fourth Annual ACM-SIAM Symposium on Discrete Algorithms"
223 .%T "Engineering a Sort Function"
224 .%J "bentley@research.att.com"