Constructs a sorted range beginning atresult consisting of elements that are found in both sorted input ranges[first1, last1) and[first2, last2). If some element is foundm times in[first1, last1) andn times in[first2, last2), the firstmin(m, n) elements will be copied from the first range toresult. The order of equivalent elements is preserved.

The behavior is undefined if

• the input ranges are not sorted with respect tocomp andproj1 orproj2, respectively, or
• the resulting range overlaps with either of the input ranges.

The function-like entities described on this page arealgorithm function objects (informally known asniebloids), that is:

• Explicit template argument lists cannot be specified when calling any of them.
• None of them are visible toargument-dependent lookup.
• When any of them are found bynormal unqualified lookup as the name to the left of the function-call operator,argument-dependent lookup is inhibited.

[edit]Parameters

[edit]Return value

{last1, last2, result_last}, whereresult_last is the end of the constructed range.

[edit]Complexity

At most\(\scriptsize 2\cdot(N_1+N_2)-1\)2·(N1+N2)-1 comparisons and applications of each projection, where\(\scriptsize N_1\)N1 and\(\scriptsize N_2\)N2 areranges::distance(first1, last1) andranges::distance(first2, last2), respectively.

[edit]Possible implementation

struct set_intersection_fn{template<std::input_iterator I1,std::sentinel_for<I1> S1,std::input_iterator I2,std::sentinel_for<I2> S2,std::weakly_incrementable O,class Comp=ranges::less,class Proj1=std::identity,class Proj2=std::identity>    requiresstd::mergeable<I1, I2, O, Comp, Proj1, Proj2>constexpr ranges::set_intersection_result<I1, I2, O>        operator()(I1 first1, S1 last1, I2 first2, S2 last2,                   O result, Comp comp={},                   Proj1 proj1={}, Proj2 proj2={})const{while(!(first1== last1 or first2== last2)){if(std::invoke(comp,std::invoke(proj1,*first1),std::invoke(proj2,*first2)))++first1;elseif(std::invoke(comp,std::invoke(proj2,*first2),std::invoke(proj1,*first1)))++first2;else*result=*first1,++first1,++first2,++result;}return{ranges::next(std::move(first1), std::move(last1)),ranges::next(std::move(first2), std::move(last2)),                std::move(result)};} template<ranges::input_range R1,ranges::input_range R2,std::weakly_incrementable O,class Comp=ranges::less,class Proj1=std::identity,class Proj2=std::identity>    requiresstd::mergeable<ranges::iterator_t<R1>,ranges::iterator_t<R2>,                            O, Comp, Proj1, Proj2>constexpr ranges::set_intersection_result<ranges::borrowed_iterator_t<R1>,ranges::borrowed_iterator_t<R2>, O>        operator()(R1&& r1, R2&& r2, O result, Comp comp={},                   Proj1 proj1={}, Proj2 proj2={})const{return(*this)(ranges::begin(r1),ranges::end(r1),ranges::begin(r2),ranges::end(r2),                       std::move(result), std::move(comp),                       std::move(proj1), std::move(proj2));}}; inlineconstexpr set_intersection_fn set_intersection{};

[edit]Example

#include <algorithm>#include <iostream>#include <iterator>#include <vector> void print(constauto& v,constauto& rem){std::cout<<"{ ";for(constauto& e: v)std::cout<< e<<' ';std::cout<<'}'<< rem;} int main(){constauto in1={1,2,2,3,4,5,6};constauto in2={2,2,3,3,5,7};std::vector<int> out{};     std::ranges::set_intersection(in1, in2,std::back_inserter(out));     print(in1," ∩ "), print(in2," = "), print(out,"\n");}

{ 1 2 2 3 4 5 6 } ∩ { 2 2 3 3 5 7 } = { 2 2 3 5 }

[edit]See also

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