std::set_union
Defined in header
<algorithm>
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template< class InputIt1, class InputIt2, class OutputIt >
OutputIt set_union( InputIt1 first1, InputIt1 last1, |
(1) | |
template< class InputIt1, class InputIt2,
class OutputIt, class Compare > |
(2) | |
Constructs a sorted range beginning at d_first
consisting of all elements present in one or both sorted ranges [first1, last1)
and [first2, last2)
.
comp
If some element is found m
times in [first1, last1)
and n
times in [first2, last2)
, then all m
elements will be copied from [first1, last1)
to d_first
, preserving order, and then exactly std::max(n-m, 0) elements will be copied from [first2, last2)
to d_first
, also preserving order.
The resulting range cannot overlap with either of the input ranges.
Contents |
[edit] Parameters
first1, last1 | - | the first input sorted range |
first2, last2 | - | the second input sorted range |
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: bool cmp(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function object must not modify the objects passed to it. |
Type requirements | ||
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InputIt1 must meet the requirements of InputIterator .
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InputIt2 must meet the requirements of InputIterator .
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OutputIt must meet the requirements of OutputIterator .
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[edit] Return value
Iterator past the end of the constructed range.
[edit] Complexity
At most 2·(N1+N2-1) comparisons, where N1 = std::distance(first1, last1) and N2 = std::distance(first2, last2).
[edit] Possible implementation
First version |
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template<class InputIt1, class InputIt2, class OutputIt> OutputIt set_union(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2, OutputIt d_first) { for (; first1 != last1; ++d_first) { if (first2 == last2) return std::copy(first1, last1, d_first); if (*first2 < *first1) { *d_first = *first2++; } else { *d_first = *first1; if (!(*first1 < *first2)) ++first2; ++first1; } } return std::copy(first2, last2, d_first); } |
Second version |
template<class InputIt1, class InputIt2, class OutputIt, class Compare> OutputIt set_union(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2, OutputIt d_first, Compare comp) { for (; first1 != last1; ++d_first) { if (first2 == last2) return std::copy(first1, last1, d_first); if (comp(*first2, *first1)) { *d_first = *first2++; } else { *d_first = *first1; if (!comp(*first1, *first2)) ++first2; ++first1; } } return std::copy(first2, last2, d_first); } |
[edit] Example
Example with vectors :
#include <vector> #include <set> #include <iostream> #include <algorithm> #include <iterator> int main() { std::vector<int> v1 = {1, 2, 3, 4, 5}; std::vector<int> v2 = { 3, 4, 5, 6, 7}; std::vector<int> dest1; std::set_union(v1.begin(), v1.end(), v2.begin(), v2.end(), std::back_inserter(dest1)); for (const auto &i : dest1) { std::cout << i << ' '; } std::cout << '\n'; }
Output:
1 2 3 4 5 6 7
[edit] See also
returns true if one set is a subset of another (function template) |
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computes the difference between two sets (function template) |
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computes the intersection of two sets (function template) |
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computes the symmetric difference between two sets (function template) |