libstdc++

ext/algorithm
Go to the documentation of this file.
1 // Algorithm extensions -*- C++ -*-
2
3 // Copyright (C) 2001-2013 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation. Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose. It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation. Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose. It is provided "as is" without express or implied warranty.
49 */
50
51 /** @file ext/algorithm
52 * This file is a GNU extension to the Standard C++ Library (possibly
53 * containing extensions from the HP/SGI STL subset).
54 */
55
56 #ifndef _EXT_ALGORITHM
57 #define _EXT_ALGORITHM 1
58
59 #pragma GCC system_header
60
61 #include <algorithm>
62
63 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
64 {
65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
66
67 using std::ptrdiff_t;
68 using std::min;
69 using std::pair;
70 using std::input_iterator_tag;
71 using std::random_access_iterator_tag;
72 using std::iterator_traits;
73
74 //--------------------------------------------------
75 // copy_n (not part of the C++ standard)
76
77 template<typename _InputIterator, typename _Size, typename _OutputIterator>
78 pair<_InputIterator, _OutputIterator>
79 __copy_n(_InputIterator __first, _Size __count,
80 _OutputIterator __result,
81 input_iterator_tag)
82 {
83 for ( ; __count > 0; --__count)
84 {
85 *__result = *__first;
86 ++__first;
87 ++__result;
88 }
89 return pair<_InputIterator, _OutputIterator>(__first, __result);
90 }
91
92 template<typename _RAIterator, typename _Size, typename _OutputIterator>
93 inline pair<_RAIterator, _OutputIterator>
94 __copy_n(_RAIterator __first, _Size __count,
95 _OutputIterator __result,
96 random_access_iterator_tag)
97 {
98 _RAIterator __last = __first + __count;
99 return pair<_RAIterator, _OutputIterator>(__last, std::copy(__first,
100 __last,
101 __result));
102 }
103
104 /**
105 * @brief Copies the range [first,first+count) into [result,result+count).
106 * @param __first An input iterator.
107 * @param __count The number of elements to copy.
108 * @param __result An output iterator.
109 * @return A std::pair composed of first+count and result+count.
110 *
111 * This is an SGI extension.
112 * This inline function will boil down to a call to @c memmove whenever
113 * possible. Failing that, if random access iterators are passed, then the
114 * loop count will be known (and therefore a candidate for compiler
115 * optimizations such as unrolling).
116 * @ingroup SGIextensions
117 */
118 template<typename _InputIterator, typename _Size, typename _OutputIterator>
119 inline pair<_InputIterator, _OutputIterator>
120 copy_n(_InputIterator __first, _Size __count, _OutputIterator __result)
121 {
122 // concept requirements
123 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
124 __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
125 typename iterator_traits<_InputIterator>::value_type>)
126
127 return __gnu_cxx::__copy_n(__first, __count, __result,
128 std::__iterator_category(__first));
129 }
130
131 template<typename _InputIterator1, typename _InputIterator2>
132 int
133 __lexicographical_compare_3way(_InputIterator1 __first1,
134 _InputIterator1 __last1,
135 _InputIterator2 __first2,
136 _InputIterator2 __last2)
137 {
138 while (__first1 != __last1 && __first2 != __last2)
139 {
140 if (*__first1 < *__first2)
141 return -1;
142 if (*__first2 < *__first1)
143 return 1;
144 ++__first1;
145 ++__first2;
146 }
147 if (__first2 == __last2)
148 return !(__first1 == __last1);
149 else
150 return -1;
151 }
152
153 inline int
154 __lexicographical_compare_3way(const unsigned char* __first1,
155 const unsigned char* __last1,
156 const unsigned char* __first2,
157 const unsigned char* __last2)
158 {
159 const ptrdiff_t __len1 = __last1 - __first1;
160 const ptrdiff_t __len2 = __last2 - __first2;
161 const int __result = __builtin_memcmp(__first1, __first2,
162 min(__len1, __len2));
163 return __result != 0 ? __result
164 : (__len1 == __len2 ? 0 : (__len1 < __len2 ? -1 : 1));
165 }
166
167 inline int
168 __lexicographical_compare_3way(const char* __first1, const char* __last1,
169 const char* __first2, const char* __last2)
170 {
171 #if CHAR_MAX == SCHAR_MAX
172 return __lexicographical_compare_3way((const signed char*) __first1,
173 (const signed char*) __last1,
174 (const signed char*) __first2,
175 (const signed char*) __last2);
176 #else
177 return __lexicographical_compare_3way((const unsigned char*) __first1,
178 (const unsigned char*) __last1,
179 (const unsigned char*) __first2,
180 (const unsigned char*) __last2);
181 #endif
182 }
183
184 /**
185 * @brief @c memcmp on steroids.
186 * @param __first1 An input iterator.
187 * @param __last1 An input iterator.
188 * @param __first2 An input iterator.
189 * @param __last2 An input iterator.
190 * @return An int, as with @c memcmp.
191 *
192 * The return value will be less than zero if the first range is
193 * <em>lexigraphically less than</em> the second, greater than zero
194 * if the second range is <em>lexigraphically less than</em> the
195 * first, and zero otherwise.
196 * This is an SGI extension.
197 * @ingroup SGIextensions
198 */
199 template<typename _InputIterator1, typename _InputIterator2>
200 int
201 lexicographical_compare_3way(_InputIterator1 __first1,
202 _InputIterator1 __last1,
203 _InputIterator2 __first2,
204 _InputIterator2 __last2)
205 {
206 // concept requirements
207 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator1>)
208 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator2>)
209 __glibcxx_function_requires(_LessThanComparableConcept<
210 typename iterator_traits<_InputIterator1>::value_type>)
211 __glibcxx_function_requires(_LessThanComparableConcept<
212 typename iterator_traits<_InputIterator2>::value_type>)
213 __glibcxx_requires_valid_range(__first1, __last1);
214 __glibcxx_requires_valid_range(__first2, __last2);
215
216 return __lexicographical_compare_3way(__first1, __last1, __first2,
217 __last2);
218 }
219
220 // count and count_if: this version, whose return type is void, was present
221 // in the HP STL, and is retained as an extension for backward compatibility.
222 template<typename _InputIterator, typename _Tp, typename _Size>
223 void
224 count(_InputIterator __first, _InputIterator __last,
225 const _Tp& __value,
226 _Size& __n)
227 {
228 // concept requirements
229 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
230 __glibcxx_function_requires(_EqualityComparableConcept<
231 typename iterator_traits<_InputIterator>::value_type >)
232 __glibcxx_function_requires(_EqualityComparableConcept<_Tp>)
233 __glibcxx_requires_valid_range(__first, __last);
234
235 for ( ; __first != __last; ++__first)
236 if (*__first == __value)
237 ++__n;
238 }
239
240 template<typename _InputIterator, typename _Predicate, typename _Size>
241 void
242 count_if(_InputIterator __first, _InputIterator __last,
243 _Predicate __pred,
244 _Size& __n)
245 {
246 // concept requirements
247 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
248 __glibcxx_function_requires(_UnaryPredicateConcept<_Predicate,
249 typename iterator_traits<_InputIterator>::value_type>)
250 __glibcxx_requires_valid_range(__first, __last);
251
252 for ( ; __first != __last; ++__first)
253 if (__pred(*__first))
254 ++__n;
255 }
256
257 // random_sample and random_sample_n (extensions, not part of the standard).
258
259 /**
260 * This is an SGI extension.
261 * @ingroup SGIextensions
262 * @doctodo
263 */
264 template<typename _ForwardIterator, typename _OutputIterator,
265 typename _Distance>
266 _OutputIterator
267 random_sample_n(_ForwardIterator __first, _ForwardIterator __last,
268 _OutputIterator __out, const _Distance __n)
269 {
270 // concept requirements
271 __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
272 __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
273 typename iterator_traits<_ForwardIterator>::value_type>)
274 __glibcxx_requires_valid_range(__first, __last);
275
276 _Distance __remaining = std::distance(__first, __last);
277 _Distance __m = min(__n, __remaining);
278
279 while (__m > 0)
280 {
281 if ((std::rand() % __remaining) < __m)
282 {
283 *__out = *__first;
284 ++__out;
285 --__m;
286 }
287 --__remaining;
288 ++__first;
289 }
290 return __out;
291 }
292
293 /**
294 * This is an SGI extension.
295 * @ingroup SGIextensions
296 * @doctodo
297 */
298 template<typename _ForwardIterator, typename _OutputIterator,
299 typename _Distance, typename _RandomNumberGenerator>
300 _OutputIterator
301 random_sample_n(_ForwardIterator __first, _ForwardIterator __last,
302 _OutputIterator __out, const _Distance __n,
303 _RandomNumberGenerator& __rand)
304 {
305 // concept requirements
306 __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
307 __glibcxx_function_requires(_OutputIteratorConcept<_OutputIterator,
308 typename iterator_traits<_ForwardIterator>::value_type>)
309 __glibcxx_function_requires(_UnaryFunctionConcept<
310 _RandomNumberGenerator, _Distance, _Distance>)
311 __glibcxx_requires_valid_range(__first, __last);
312
313 _Distance __remaining = std::distance(__first, __last);
314 _Distance __m = min(__n, __remaining);
315
316 while (__m > 0)
317 {
318 if (__rand(__remaining) < __m)
319 {
320 *__out = *__first;
321 ++__out;
322 --__m;
323 }
324 --__remaining;
325 ++__first;
326 }
327 return __out;
328 }
329
330 template<typename _InputIterator, typename _RandomAccessIterator,
331 typename _Distance>
332 _RandomAccessIterator
333 __random_sample(_InputIterator __first, _InputIterator __last,
334 _RandomAccessIterator __out,
335 const _Distance __n)
336 {
337 _Distance __m = 0;
338 _Distance __t = __n;
339 for ( ; __first != __last && __m < __n; ++__m, ++__first)
340 __out[__m] = *__first;
341
342 while (__first != __last)
343 {
344 ++__t;
345 _Distance __M = std::rand() % (__t);
346 if (__M < __n)
347 __out[__M] = *__first;
348 ++__first;
349 }
350 return __out + __m;
351 }
352
353 template<typename _InputIterator, typename _RandomAccessIterator,
354 typename _RandomNumberGenerator, typename _Distance>
355 _RandomAccessIterator
356 __random_sample(_InputIterator __first, _InputIterator __last,
357 _RandomAccessIterator __out,
358 _RandomNumberGenerator& __rand,
359 const _Distance __n)
360 {
361 // concept requirements
362 __glibcxx_function_requires(_UnaryFunctionConcept<
363 _RandomNumberGenerator, _Distance, _Distance>)
364
365 _Distance __m = 0;
366 _Distance __t = __n;
367 for ( ; __first != __last && __m < __n; ++__m, ++__first)
368 __out[__m] = *__first;
369
370 while (__first != __last)
371 {
372 ++__t;
373 _Distance __M = __rand(__t);
374 if (__M < __n)
375 __out[__M] = *__first;
376 ++__first;
377 }
378 return __out + __m;
379 }
380
381 /**
382 * This is an SGI extension.
383 * @ingroup SGIextensions
384 * @doctodo
385 */
386 template<typename _InputIterator, typename _RandomAccessIterator>
387 inline _RandomAccessIterator
388 random_sample(_InputIterator __first, _InputIterator __last,
389 _RandomAccessIterator __out_first,
390 _RandomAccessIterator __out_last)
391 {
392 // concept requirements
393 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
394 __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
395 _RandomAccessIterator>)
396 __glibcxx_requires_valid_range(__first, __last);
397 __glibcxx_requires_valid_range(__out_first, __out_last);
398
399 return __random_sample(__first, __last,
400 __out_first, __out_last - __out_first);
401 }
402
403 /**
404 * This is an SGI extension.
405 * @ingroup SGIextensions
406 * @doctodo
407 */
408 template<typename _InputIterator, typename _RandomAccessIterator,
409 typename _RandomNumberGenerator>
410 inline _RandomAccessIterator
411 random_sample(_InputIterator __first, _InputIterator __last,
412 _RandomAccessIterator __out_first,
413 _RandomAccessIterator __out_last,
414 _RandomNumberGenerator& __rand)
415 {
416 // concept requirements
417 __glibcxx_function_requires(_InputIteratorConcept<_InputIterator>)
418 __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
419 _RandomAccessIterator>)
420 __glibcxx_requires_valid_range(__first, __last);
421 __glibcxx_requires_valid_range(__out_first, __out_last);
422
423 return __random_sample(__first, __last,
424 __out_first, __rand,
425 __out_last - __out_first);
426 }
427
428 #if __cplusplus >= 201103L
429 using std::is_heap;
430 #else
431 /**
432 * This is an SGI extension.
433 * @ingroup SGIextensions
434 * @doctodo
435 */
436 template<typename _RandomAccessIterator>
437 inline bool
438 is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
439 {
440 // concept requirements
441 __glibcxx_function_requires(_RandomAccessIteratorConcept<
442 _RandomAccessIterator>)
443 __glibcxx_function_requires(_LessThanComparableConcept<
444 typename iterator_traits<_RandomAccessIterator>::value_type>)
445 __glibcxx_requires_valid_range(__first, __last);
446
447 return std::__is_heap(__first, __last - __first);
448 }
449
450 /**
451 * This is an SGI extension.
452 * @ingroup SGIextensions
453 * @doctodo
454 */
455 template<typename _RandomAccessIterator, typename _StrictWeakOrdering>
456 inline bool
457 is_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
458 _StrictWeakOrdering __comp)
459 {
460 // concept requirements
461 __glibcxx_function_requires(_RandomAccessIteratorConcept<
462 _RandomAccessIterator>)
463 __glibcxx_function_requires(_BinaryPredicateConcept<_StrictWeakOrdering,
464 typename iterator_traits<_RandomAccessIterator>::value_type,
465 typename iterator_traits<_RandomAccessIterator>::value_type>)
466 __glibcxx_requires_valid_range(__first, __last);
467
468 return std::__is_heap(__first, __comp, __last - __first);
469 }
470 #endif
471
472 #if __cplusplus >= 201103L
473 using std::is_sorted;
474 #else
475 // is_sorted, a predicated testing whether a range is sorted in
476 // nondescending order. This is an extension, not part of the C++
477 // standard.
478
479 /**
480 * This is an SGI extension.
481 * @ingroup SGIextensions
482 * @doctodo
483 */
484 template<typename _ForwardIterator>
485 bool
486 is_sorted(_ForwardIterator __first, _ForwardIterator __last)
487 {
488 // concept requirements
489 __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
490 __glibcxx_function_requires(_LessThanComparableConcept<
491 typename iterator_traits<_ForwardIterator>::value_type>)
492 __glibcxx_requires_valid_range(__first, __last);
493
494 if (__first == __last)
495 return true;
496
497 _ForwardIterator __next = __first;
498 for (++__next; __next != __last; __first = __next, ++__next)
499 if (*__next < *__first)
500 return false;
501 return true;
502 }
503
504 /**
505 * This is an SGI extension.
506 * @ingroup SGIextensions
507 * @doctodo
508 */
509 template<typename _ForwardIterator, typename _StrictWeakOrdering>
510 bool
511 is_sorted(_ForwardIterator __first, _ForwardIterator __last,
512 _StrictWeakOrdering __comp)
513 {
514 // concept requirements
515 __glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
516 __glibcxx_function_requires(_BinaryPredicateConcept<_StrictWeakOrdering,
517 typename iterator_traits<_ForwardIterator>::value_type,
518 typename iterator_traits<_ForwardIterator>::value_type>)
519 __glibcxx_requires_valid_range(__first, __last);
520
521 if (__first == __last)
522 return true;
523
524 _ForwardIterator __next = __first;
525 for (++__next; __next != __last; __first = __next, ++__next)
526 if (__comp(*__next, *__first))
527 return false;
528 return true;
529 }
530 #endif // C++11
531
532 /**
533 * @brief Find the median of three values.
534 * @param __a A value.
535 * @param __b A value.
536 * @param __c A value.
537 * @return One of @p a, @p b or @p c.
538 *
539 * If @c {l,m,n} is some convolution of @p {a,b,c} such that @c l<=m<=n
540 * then the value returned will be @c m.
541 * This is an SGI extension.
542 * @ingroup SGIextensions
543 */
544 template<typename _Tp>
545 const _Tp&
546 __median(const _Tp& __a, const _Tp& __b, const _Tp& __c)
547 {
548 // concept requirements
549 __glibcxx_function_requires(_LessThanComparableConcept<_Tp>)
550 if (__a < __b)
551 if (__b < __c)
552 return __b;
553 else if (__a < __c)
554 return __c;
555 else
556 return __a;
557 else if (__a < __c)
558 return __a;
559 else if (__b < __c)
560 return __c;
561 else
562 return __b;
563 }
564
565 /**
566 * @brief Find the median of three values using a predicate for comparison.
567 * @param __a A value.
568 * @param __b A value.
569 * @param __c A value.
570 * @param __comp A binary predicate.
571 * @return One of @p a, @p b or @p c.
572 *
573 * If @c {l,m,n} is some convolution of @p {a,b,c} such that @p comp(l,m)
574 * and @p comp(m,n) are both true then the value returned will be @c m.
575 * This is an SGI extension.
576 * @ingroup SGIextensions
577 */
578 template<typename _Tp, typename _Compare>
579 const _Tp&
580 __median(const _Tp& __a, const _Tp& __b, const _Tp& __c, _Compare __comp)
581 {
582 // concept requirements
583 __glibcxx_function_requires(_BinaryFunctionConcept<_Compare, bool,
584 _Tp, _Tp>)
585 if (__comp(__a, __b))
586 if (__comp(__b, __c))
587 return __b;
588 else if (__comp(__a, __c))
589 return __c;
590 else
591 return __a;
592 else if (__comp(__a, __c))
593 return __a;
594 else if (__comp(__b, __c))
595 return __c;
596 else
597 return __b;
598 }
599
600 _GLIBCXX_END_NAMESPACE_VERSION
601 } // namespace
602
603 #endif /* _EXT_ALGORITHM */