Computes symmetric difference of two sorted ranges: the elements that are found in either of the ranges, but not in both of them are copied to the range beginning atresult. The resulting range is also sorted.

If some element is foundm times in[first1, last1) andn times in[first2, last2), it will be copied toresult exactly│m - n│ times. Ifm > n, then the lastm - n of those elements are copied from[first1, last1), otherwise the lastn - m elements are copied from[first2, last2). The resulting range cannot overlap with either of the input ranges.

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_symmetric_difference_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_symmetric_difference_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))){*result=*first1;++first1;++result;}elseif(std::invoke(comp,std::invoke(proj2,*first2),std::invoke(proj1,*first1))){*result=*first2;++first2;++result;}else{++first1;++first2;}}auto res1{ranges::copy(std::move(first1), std::move(last1), std::move(result))};auto res2{ranges::copy(std::move(first2), std::move(last2), std::move(res1.out))};return{std::move(res1.in), std::move(res2.in), std::move(res2.out)};} 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_symmetric_difference_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_symmetric_difference_fn set_symmetric_difference{};

[edit]Example

#include <algorithm>#include <iostream>#include <iterator>#include <vector> void visualize_this(constauto& v,int min=1,int max=9){for(auto i{min}; i<= max;++i){        std::ranges::binary_search(v, i)?std::cout<< i:std::cout<<'.';std::cout<<' ';}std::cout<<'\n';} int main(){constauto in1={1,3,4,6,7,9};constauto in2={1,4,5,6,9}; std::vector<int> out{};     std::ranges::set_symmetric_difference(in1, in2,std::back_inserter(out));     visualize_this(in1);    visualize_this(in2);    visualize_this(out);}

1 . 3 4 . 6 7 . 91 . . 4 5 6 . . 9. . 3 . 5 . 7 . .

[edit]See also

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