std::unordered_set<Key,Hash,KeyEqual,Allocator>::merge

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

span (C++20)

 

std::unordered_set

Member functions

unordered_set::unordered_set

unordered_set::~unordered_set

unordered_set::operator=

unordered_set::get_allocator

Iterators

unordered_set::beginunordered_set::cbegin

unordered_set::endunordered_set::cend

Capacity

unordered_set::empty

unordered_set::size

unordered_set::max_size

Modifiers

unordered_set::clear

unordered_set::insert

unordered_set::emplace

unordered_set::emplace_hint

unordered_set::erase

unordered_set::swap

unordered_set::extract (C++17)

unordered_set::merge (C++17)

Lookup

unordered_set::count

unordered_set::find

unordered_set::contains (C++20)

unordered_set::equal_range

Bucket interface

unordered_set::begin(size_type)unordered_set::cbegin(size_type)

unordered_set::end(size_type)unordered_set::cend(size_type)

unordered_set::bucket_count

unordered_set::max_bucket_count

unordered_set::bucket_size

unordered_set::bucket

Hash policy

unordered_set::load_factor

unordered_set::max_load_factor

unordered_set::rehash

unordered_set::reserve

Observers

unordered_set::hash_function

unordered_set::key_eq

Deduction guides(C++17)

 

template<class H2, class P2> void merge(std::unordered_set<Key, H2, P2, Allocator>& source);	(1)	(since C++17)
template<class H2, class P2> void merge(std::unordered_set<Key, H2, P2, Allocator>&& source);	(2)	(since C++17)
template<class H2, class P2> void merge(std::unordered_multiset<Key, H2, P2, Allocator>& source);	(3)	(since C++17)
template<class H2, class P2> void merge(std::unordered_multiset<Key, H2, P2, Allocator>&& source);	(4)	(since C++17)

Attempts to extract ("splice") each element in source and insert it into *this using the hash function and key equality predicate of *this. If there is an element in *this with key equivalent to the key of an element from source, then that element is not extracted from source. 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. Iterators referring to the transferred elements and all iterators referring to *this are invalidated. Iterators to elements remaining in source remain valid.

The behavior is undefined if get_allocator() != source.get_allocator().

Parameters

source

-

compatible container to transfer the nodes from

Return value

(none)

Complexity

Average case O(N), worst case O(N*size()+N), where N is source.size()

See also

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