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) | |
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 ); | (2) |
Constructs a sorted range beginning at d_first
consisting of elements that are found in both sorted ranges [first1, last1)
and [first2, last2)
. The first version expects both input ranges to be sorted with operator<
, the second version expects them to be sorted with the given comparison function comp
. If some element is found m
times in [first1, last1)
and n
times in [first2, last2)
, the first std::min(m, n)
elements will be copied from the first range to the destination range. The order of equivalent elements is preserved. The resulting range cannot overlap with either of the input ranges.
Parameters
first1, last1 | - | the first range of elements to examine |
first2, last2 | - | the second range of elements to examine |
comp | - | comparison function object (i.e. an object that satisfies the requirements of Compare ) which returns true if the first argument is less than (i.e. is ordered before) the second. The signature of the comparison function should be equivalent to the following:
The signature does not need to have |
Type requirements | ||
- InputIt1 must meet the requirements of InputIterator . | ||
- InputIt2 must meet the requirements of InputIterator . | ||
- OutputIt must meet the requirements of OutputIterator . |
Return value
Iterator past the end of the constructed range.
Complexity
At most 2·(N1+N2-1) comparisons, where N1= std::distance(first1, last1)
and N2= std::distance(first2, last2)
.
Possible implementation
First version |
---|
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++; } ++first2; } } return d_first; } |
Second version |
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++; } ++first2; } } return d_first; } |
Example
#include <iostream> #include <vector> #include <algorithm> #include <iterator> int main() { std::vector<int> v1{1,2,3,4,5,6,7,8}; std::vector<int> v2{ 5, 7, 9,10}; 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 << ' '; }
Output:
5 7
See also
computes the union of two sets (function template) | |
std::experimental::parallel::set_intersection
(parallelism TS) | parallelized version of std::set_intersection (function template) |
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