std::multiset<Key,Compare,Allocator>::merge
From cppreference.com
template< class C2 >
void merge( std::set<Key, C2, Allocator>& source );
|
(1) | (since C++17) |
template< class C2 >
void merge( std::set<Key, C2, Allocator>&& source );
|
(2) | (since C++17) |
template< class C2 >
void merge( std::multiset<Key, C2, Allocator>& source );
|
(3) | (since C++17) |
template< class C2 >
void merge( std::multiset<Key, C2, Allocator>&& source );
|
(4) | (since C++17) |
Attempts to extract ("splice") each element in source and insert it into *this using the comparison object of *this.
No elements are copied or moved, only the internal pointers of the container nodes are repointed. All pointers and references to the transferred elements remain valid, but now refer into *this, not into source.
The behavior is undefined if get_allocator() != source.get_allocator().
Parameters
| source | - | compatible container to transfer the nodes from |
Return value
(none)
Exceptions
Does not throw unless comparison throws.
Complexity
N * log(size() + N)), where N is source.size().
Example
Run this code
#include <iostream>
#include <set>
// print out a container
template<class Os, class K>
Os& operator<<(Os& os, const std::multiset<K>& v)
{
os << '[' << v.size() << "] {";
bool o{};
for (const auto& e : v)
os << (o ? ", " : (o = 1, " ")) << e;
return os << " }\n";
}
int main()
{
std::multiset<char>
p{'C', 'B', 'B', 'A'},
q{'E', 'D', 'E', 'C'};
std::cout << "p: " << p << "q: " << q;
p.merge(q);
std::cout << "p.merge(q);\n" << "p: " << p << "q: " << q;
}
Output:
p: [4] { A, B, B, C }
q: [4] { C, D, E, E }
p.merge(q);
p: [8] { A, B, B, C, C, D, E, E }
q: [0] { }
See also
(C++17) |
extracts nodes from the container (public member function) |
| inserts elements or nodes(since C++17) (public member function) |