153 lines
8.7 KiB
Markdown
153 lines
8.7 KiB
Markdown
[set.difference]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.8 Sorting and related operations [[alg.sorting]](alg.sorting#set.difference)
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### 26.8.7 Set operations on sorted structures [[alg.set.operations]](alg.set.operations#set.difference)
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#### 26.8.7.5 set_difference [set.difference]
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[ð](#lib:set_difference)
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`template<class InputIterator1, class InputIterator2,
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class OutputIterator>
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constexpr OutputIterator
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set_difference(InputIterator1 first1, InputIterator1 last1,
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InputIterator2 first2, InputIterator2 last2,
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OutputIterator result);
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template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
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class ForwardIterator>
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ForwardIterator
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set_difference(ExecutionPolicy&& exec,
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ForwardIterator1 first1, ForwardIterator1 last1,
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ForwardIterator2 first2, ForwardIterator2 last2,
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ForwardIterator result);
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template<class InputIterator1, class InputIterator2,
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class OutputIterator, class Compare>
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constexpr OutputIterator
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set_difference(InputIterator1 first1, InputIterator1 last1,
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InputIterator2 first2, InputIterator2 last2,
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OutputIterator result, Compare comp);
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template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
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class ForwardIterator, class Compare>
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ForwardIterator
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set_difference(ExecutionPolicy&& exec,
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ForwardIterator1 first1, ForwardIterator1 last1,
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ForwardIterator2 first2, ForwardIterator2 last2,
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ForwardIterator result, Compare comp);
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template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_iterator [iterator.concept.input]") I1, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I1> S1, [input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_iterator [iterator.concept.input]") I2, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I2> S2,
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[weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_incrementable [iterator.concept.winc]") O, class Comp = ranges::less,
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class Proj1 = identity, class Proj2 = identity>
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requires [mergeable](alg.req.mergeable#concept:mergeable "24.3.7.7 Concept mergeable [alg.req.mergeable]")<I1, I2, O, Comp, Proj1, Proj2>
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constexpr ranges::set_difference_result<I1, O>
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ranges::set_difference(I1 first1, S1 last1, I2 first2, S2 last2, O result,
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Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
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template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R2, [weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_incrementable [iterator.concept.winc]") O,
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class Comp = ranges::less, class Proj1 = identity, class Proj2 = identity>
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requires [mergeable](alg.req.mergeable#concept:mergeable "24.3.7.7 Concept mergeable [alg.req.mergeable]")<iterator_t<R1>, iterator_t<R2>, O, Comp, Proj1, Proj2>
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constexpr ranges::set_difference_result<borrowed_iterator_t<R1>, O>
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ranges::set_difference(R1&& r1, R2&& r2, O result,
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Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
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template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_access_iterator [iterator.concept.random.access]") I1, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<I1> S1,
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[random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_access_iterator [iterator.concept.random.access]") I2, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<I2> S2,
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[random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_access_iterator [iterator.concept.random.access]") O, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<O> OutS, class Comp = ranges::less,
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class Proj1 = identity, class Proj2 = identity>
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requires [mergeable](alg.req.mergeable#concept:mergeable "24.3.7.7 Concept mergeable [alg.req.mergeable]")<I1, I2, O, Comp, Proj1, Proj2>
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ranges::set_difference_result<I1, O>
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ranges::set_difference(Ep&& exec, I1 first1, S1 last1,
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I2 first2, S2 last2, O result, OutS result_last,
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Comp comp = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
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template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R1, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R2,
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[sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") OutR, class Comp = ranges::less,
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class Proj1 = identity, class Proj2 = identity>
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requires [mergeable](alg.req.mergeable#concept:mergeable "24.3.7.7 Concept mergeable [alg.req.mergeable]")<iterator_t<R1>, iterator_t<R2>, iterator_t<OutR>, Comp, Proj1, Proj2>
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ranges::set_difference_result<borrowed_iterator_t<R1>, borrowed_iterator_t<OutR>>
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ranges::set_difference(Ep&& exec, R1&& r1, R2&& r2, OutR&& result_r, Comp comp = {},
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Proj1 proj1 = {}, Proj2 proj2 = {});
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L10673)
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Let:
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- [(1.1)](#1.1)
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comp be less{},
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and proj1 and proj2 be identity{} for the overloads with no parameters by those names;
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- [(1.2)](#1.2)
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M be the number of elements in [first1, last1)
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that are not present in [first2, last2);
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- [(1.3)](#1.3)
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result_last be result + M for the overloads with no parameter result_last or result_r;
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- [(1.4)](#1.4)
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N be min(M, result_last - result)[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L10690)
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*Preconditions*: The ranges [first1, last1) and [first2, last2) are sorted
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with respect to comp and proj1 or proj2, respectively[.](#2.sentence-1)
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The resulting range does not overlap with either of the original ranges[.](#2.sentence-2)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L10696)
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*Effects*: Copies N elements of the range [first1, last1)
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which are not present in the range [first2, last2)
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to the range [result, result + N)[.](#3.sentence-1)
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The elements in the constructed range are sorted[.](#3.sentence-2)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L10703)
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*Returns*:
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- [(4.1)](#4.1)
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result_last for the overloads in namespace std[.](#4.1.sentence-1)
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- [(4.2)](#4.2)
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{last1, result + N} for the overloads in namespace ranges,
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if N is equal to M[.](#4.2.sentence-1)
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- [(4.3)](#4.3)
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Otherwise, {j1, result_last} for the overloads in namespace ranges,
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where the iterator j1 points to positions past the last copied or skipped elements
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in [first1, last1) and [first2, last2), respectively[.](#4.3.sentence-1)
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L10721)
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*Complexity*: At most 2 * ((last1 - first1) + (last2 - first2)) - 1 comparisons and applications of each projection[.](#5.sentence-1)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L10726)
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*Remarks*: If [first1, last1) contains m elements
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that are equivalent to each other and
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[first2, last2) contains n elements
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that are equivalent to them,
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the last max(mân,0) elements from [first1, last1)
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are copied to the output range, in order[.](#6.sentence-1)
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