NAME¶

std::multimap::merge - std::multimap::merge

Synopsis¶

template< class C2 > (1) (since C++17)
void merge( std::map<Key, T, C2, Allocator>& source );
template< class C2 > (2) (since C++17)
void merge( std::map<Key, T, C2, Allocator>&& source );
template< class C2 > (3) (since C++17)
void merge( std::multimap<Key, T, C2, Allocator>& source );
template< class C2 > (4) (since C++17)
void merge( std::multimap<Key, T, 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 <map>
#include <string>

int main()
{
std::multimap<int, std::string> ma{{1, "apple"}, {5, "pear"}, {10, "banana"}};
std::multimap<int, std::string> mb{{2, "zorro"}, {4, "batman"}, {5, "X"}, {8, "alpaca"}};
std::multimap<int, std::string> u;
u.merge(ma);
std::cout << "ma.size(): " << ma.size() << '\n';
u.merge(mb);
std::cout << "mb.size(): " << mb.size() << '\n';

for (auto const& kv : u)
std::cout << kv.first << ", " << kv.second << '\n';
}

Output:¶

ma.size(): 0
mb.size(): 0
1, apple
2, zorro
4, batman
5, pear
5, X
8, alpaca
10, banana

See also¶

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