std::ranges::set_intersection, std::ranges::set_intersection_result
| Defined in header <algorithm>
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| Call signature |
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| template< std::input_iterator I1, std::sentinel_for<I1> S1, std::input_iterator I2, std::sentinel_for<I2> S2, |
(1) | (since C++20) |
| template< ranges::input_range R1, ranges::input_range R2, std::weakly_incrementable O, class Comp = ranges::less, |
(2) | (since C++20) |
| Helper types |
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| template< class I1, class I2, class O > using set_intersection_result = ranges::in_in_out_result<I1, I2, O>; |
(3) | (since C++20) |
Constructs a sorted range beginning at result consisting of elements that are found in both sorted input ranges [first1, last1) and [first2, last2). If some element is found m times in [first1, last1) and n times in [first2, last2), the first min(m, n) elements will be copied from the first range to result. The order of equivalent elements is preserved.
comp.r1 as the first range and r2 as the second range, as if using ranges::begin(r1) as first1, ranges::end(r1) as last1, ranges::begin(r2) as first2, and ranges::end(r2) as last2.Preconditions:
- The input ranges must be sorted with respect to
compandproj1orproj2, respectively. - The resulting range cannot overlap with either of the input ranges.
The function-like entities described on this page are niebloids, that is:
- Explicit template argument lists may not be specified when calling any of them.
- None of them is visible to argument-dependent lookup.
- When one of them is found by normal unqualified lookup for the name to the left of the function-call operator, it inhibits argument-dependent lookup.
In practice, they may be implemented as function objects, or with special compiler extensions.
Contents |
[edit] Parameters
| first1, last1 | - | the first input sorted range |
| first2, last2 | - | the second input sorted range |
| result | - | the beginning of the output range |
| comp | - | comparison to apply to the projected elements |
| proj1 | - | projection to apply to the elements in the first range |
| proj2 | - | projection to apply to the elements in the second range. |
[edit] Return value
{last1, last2, result_last}, where result_last is the end of the constructed range.
[edit] Complexity
At most 2·(N₁+N₂)-1 comparisons and applications of each projection, where
N₁ = ranges::distance(first1, last1), and
N₂ = ranges::distance(first2, last2).
[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 > requires std::mergeable<I1, I2, O, Comp, Proj1, Proj2> constexpr ranges::set_union_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; else if (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 > requires std::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)); } }; inline constexpr set_intersection_fn set_intersection{}; |
[edit] Example
#include <algorithm> #include <iostream> #include <iterator> #include <vector> void print(const auto& v, const auto& rem) { std::cout << "{ "; for (const auto& e : v) std::cout << e << ' '; std::cout << "}" << rem; } int main() { const auto in1 = {1, 2, 2, 3, 4, 5, 6 }; const auto 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"); }
Output:
{ 1 2 2 3 4 5 6 } ∩ { 2 2 3 3 5 7 } = { 2 2 3 5 }[edit] See also
| (C++20) |
computes the union of two sets (niebloid) |
| (C++20) |
computes the difference between two sets (niebloid) |
| computes the symmetric difference between two sets (niebloid) | |
| (C++20) |
returns true if one sequence is a subsequence of another (niebloid) |
| computes the intersection of two sets (function template) |
