std::multimap<Key,T,Compare,Allocator>::merge

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Iterator invalidation

Member function table

Non-member function table

 

std::multimap

Member functions

multimap::multimap

multimap::~multimap

multimap::operator=

multimap::get_allocator

Iterators

multimap::beginmultimap::cbegin (C++11)

multimap::endmultimap::cend (C++11)

multimap::rbeginmultimap::crbegin (C++11)

multimap::rendmultimap::crend (C++11)

Capacity

multimap::empty

multimap::size

multimap::max_size

Modifiers

multimap::clear

multimap::insert

multimap::insert_range (C++23)

multimap::emplace (C++11)

multimap::emplace_hint (C++11)

multimap::erase

multimap::swap

multimap::extract (C++17)

multimap::merge (C++17)

Lookup

multimap::count

multimap::find

multimap::contains (C++20)

multimap::equal_range

multimap::lower_bound

multimap::upper_bound

Observers

multimap::key_comp

multimap::value_comp

Non-member functions

std::swap

erase_if (C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

Deduction guides(C++17)

 

template<class C2> void merge( std::map<Key, T, C2, Allocator>& source );	(1)	(since C++17)
template<class C2> void merge( std::map<Key, T, C2, Allocator>&& source );	(2)	(since C++17)
template<class C2> void merge( std::multimap<Key, T, C2, Allocator>& source );	(3)	(since C++17)
template<class C2> void merge( std::multimap<Key, T, 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 <map>
#include <iostream>
#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 (C++17)	extracts nodes from the container (public member function)
insert	inserts elements or nodes (since C++17) (public member function)