std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge (3) - Linux Manuals

std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge: std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge

NAME

std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge - std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge

Synopsis


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


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()

Example


 This section is incomplete
 Reason: no example

See also


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

Pages related to std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::merge