Movatterモバイル変換

[0]ホーム
URL:

cppreference.com
Namespaces
Variants
    Actions

      std::set_intersection

      From cppreference.com
      <cpp‎ |algorithm
       
       
      Algorithm library
      Constrained algorithms and algorithms on ranges(C++20)
      Constrained algorithms, e.g.ranges::copy,ranges::sort, ...
      Execution policies(C++17)
      Sorting and related operations
      Partitioning operations
      Sorting operations
      Binary search operations
      (on partitioned ranges)
      Set operations (on sorted ranges)
      set_intersection
      Merge operations (on sorted ranges)
      Heap operations
      Minimum/maximum operations
      (C++11)
      (C++17)
      Lexicographical comparison operations
      Permutation operations
      C library
      Numeric operations
      Operations on uninitialized memory
       
      Defined in header<algorithm>
      template<class InputIt1,class InputIt2,class OutputIt>

      OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
                                 InputIt2 first2, InputIt2 last2,

                                 OutputIt d_first);
      		 (1)(constexpr since C++20)
      template<class ExecutionPolicy,

               class ForwardIt1,class ForwardIt2,class ForwardIt3>
      ForwardIt3 set_intersection( ExecutionPolicy&& policy,
                                   ForwardIt1 first1, ForwardIt1 last1,
                                   ForwardIt2 first2, ForwardIt2 last2,

                                   ForwardIt3 d_first);
      		 (2)(since C++17)
      template<class InputIt1,class InputIt2,

               class OutputIt,class Compare>
      OutputIt set_intersection( InputIt1 first1, InputIt1 last1,
                                 InputIt2 first2, InputIt2 last2,

                                 OutputIt d_first, Compare comp);
      		 (3)(constexpr since C++20)
      template<class ExecutionPolicy,

               class ForwardIt1,class ForwardIt2,
               class ForwardIt3,class Compare>
      ForwardIt3 set_intersection( ExecutionPolicy&& policy,
                                   ForwardIt1 first1, ForwardIt1 last1,
                                   ForwardIt2 first2, ForwardIt2 last2,

                                   ForwardIt3 d_first, Compare comp);
      		 (4)(since C++17)

      Constructs a sorted range beginning atd_first consisting of elements that are found in both sorted ranges[first1, last1) and[first2, last2).

      If[first1, last1) containsm elements that are equivalent to each other and[first2, last2) containsn elements that are equivalent to them, the firststd::min(m, n) elements will be copied from[first1, last1) to the output range, preserving order.

      1) If[first1, last1) or[first2, last2) is notsorted with respect tooperator<(until C++20)std::less{}(since C++20), the behavior is undefined.
      3) If[first1, last1) or[first2, last2) is not sorted with respect tocomp, the behavior is undefined.
      2,4) Same as(1,3), but executed according topolicy.
      These overloads participate in overload resolution only if all following conditions are satisfied:

      std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> istrue.

      		(until C++20)

      std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>> istrue.

      		(since C++20)

      If the output range overlaps with[first1, last1) or[first2, last2), the behavior is undefined.

      Contents

      [edit]Parameters

      first1, last1 - the pair of iterators defining the first sortedrange of elements to examine
      first2, last2 - the pair of iterators defining the second sortedrange of elements to examine
      d_first - the beginning of the output range
      policy - theexecution policy to use
      comp - comparison function object (i.e. an object that satisfies the requirements ofCompare) which returns ​true if the first argument isless than (i.e. is orderedbefore) the second.

      The signature of the comparison function should be equivalent to the following:

      bool cmp(const Type1& a,const Type2& b);

      While the signature does not need to haveconst&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const)Type1 andType2 regardless ofvalue category (thus,Type1& is not allowed, nor isType1 unless forType1 a move is equivalent to a copy(since C++11)).
      The typesType1 andType2 must be such that objects of typesInputIt1 andInputIt2 can be dereferenced and then implicitly converted to bothType1 andType2.​

      Type requirements
      -
      InputIt1, InputIt2 must meet the requirements ofLegacyInputIterator.
      -
      OutputIt must meet the requirements ofLegacyOutputIterator.
      -
      ForwardIt1, ForwardIt2, ForwardIt3 must meet the requirements ofLegacyForwardIterator.
      -
      Compare must meet the requirements ofCompare.

      [edit]Return value

      Iterator past the end of the constructed range.

      [edit]Complexity

      Given\(\scriptsize N_1\)N1 asstd::distance(first1, last1) and\(\scriptsize N_2\)N2 asstd::distance(first2, last2):

      1,2) At most\(\scriptsize 2 \cdot (N_1+N_2)-1\)2⋅(N1+N2)-1 comparisons usingoperator<(until C++20)std::less{}(since C++20).
      3,4) At most\(\scriptsize 2 \cdot (N_1+N_2)-1\)2⋅(N1+N2)-1 applications of the comparison functioncomp.

      [edit]Exceptions

      The overloads with a template parameter namedExecutionPolicy report errors as follows:

      • If execution of a function invoked as part of the algorithm throws an exception andExecutionPolicy is one of thestandard policies,std::terminate is called. For any otherExecutionPolicy, the behavior is implementation-defined.
      • If the algorithm fails to allocate memory,std::bad_alloc is thrown.

      [edit]Possible implementation

      set_intersection (1)
      template<class InputIt1,class InputIt2,class OutputIt>OutputIt set_intersection(InputIt1 first1, InputIt1 last1,                          InputIt2 first2, InputIt2 last2, OutputIt d_first){while(first1!= last1&& first2!= last2){if(*first1<*first2)++first1;else{if(!(*first2<*first1))*d_first++=*first1++;// *first1 and *first2 are equivalent.++first2;}}return d_first;}
      set_intersection (3)
      template<class InputIt1,class InputIt2,class OutputIt,class Compare>OutputIt set_intersection(InputIt1 first1, InputIt1 last1,                          InputIt2 first2, InputIt2 last2, OutputIt d_first, Compare comp){while(first1!= last1&& first2!= last2){if(comp(*first1,*first2))++first1;else{if(!comp(*first2,*first1))*d_first++=*first1++;// *first1 and *first2 are equivalent.++first2;}}return d_first;}

      [edit]Example

      Run this code
      #include <algorithm>#include <iostream>#include <iterator>#include <vector> int main(){std::vector<int> v1{7,2,3,4,5,6,7,8};std::vector<int> v2{5,7,9,7};std::sort(v1.begin(), v1.end());std::sort(v2.begin(), v2.end()); std::vector<int> v_intersection;    std::set_intersection(v1.begin(), v1.end(), v2.begin(), v2.end(),std::back_inserter(v_intersection)); for(int n: v_intersection)std::cout<< n<<' ';std::cout<<'\n';}

      Output:

      5 7 7

      [edit]Defect reports

      The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

      DRApplied toBehavior as publishedCorrect behavior
      LWG 291C++98it was unspecified how to handle equivalent elements in the input rangesspecified

      [edit]See also

      computes the union of two sets
      (function template)[edit]
      computes the intersection of two sets
      (algorithm function object)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/algorithm/set_intersection&oldid=180581"
      [8]ページ先頭
      ©2009-2025 Movatter.jp