NAME¶

std::multiset::merge - std::multiset::merge

Synopsis¶

template<class C2> (1) (since C++17)
void merge( std::set<Key, C2, Allocator>& source );
template<class C2> (2) (since C++17)
void merge( std::set<Key, C2, Allocator>&& source );
template<class C2> (3) (since C++17)
void merge( std::multiset<Key, C2, Allocator>& source );
template<class C2> (4) (since C++17)
void merge( std::multiset<Key, C2, Allocator>&& source );

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¶

extract extracts nodes from the container
(C++17) (public member function)
inserts elements
insert or nodes
(since C++17)
(public member function)