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 | ||
-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) | |
| computes the difference between two sets (function template) | |
| computes the intersection of two sets (function template) | |
| computes the symmetric difference between two sets (function template) |