std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>::reserve

 

C++

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Feature test macros (C++20)

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Concepts library (C++20)

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Ranges library (C++20)

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Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

deque

forward_list (C++11)

list

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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

Views

span (C++20)

 

std::unordered_multimap

Member functions

unordered_multimap::unordered_multimap

unordered_multimap::~unordered_multimap

unordered_multimap::operator=

unordered_multimap::get_allocator

Iterators

unordered_multimap::beginunordered_multimap::cbegin

unordered_multimap::endunordered_multimap::cend

Capacity

unordered_multimap::empty

unordered_multimap::size

unordered_multimap::max_size

Modifiers

unordered_multimap::clear

unordered_multimap::insert

unordered_multimap::emplace

unordered_multimap::emplace_hint

unordered_multimap::erase

unordered_multimap::swap

unordered_multimap::extract (C++17)

unordered_multimap::merge (C++17)

Lookup

unordered_multimap::count

unordered_multimap::find

unordered_multimap::contains (C++20)

unordered_multimap::equal_range

Bucket interface

unordered_multimap::begin(size_type)unordered_multimap::cbegin(size_type)

unordered_multimap::end(size_type)unordered_multimap::cend(size_type)

unordered_multimap::bucket_count

unordered_multimap::max_bucket_count

unordered_multimap::bucket_size

unordered_multimap::bucket

Hash policy

unordered_multimap::load_factor

unordered_multimap::max_load_factor

unordered_multimap::rehash

unordered_multimap::reserve

Observers

unordered_multimap::hash_function

unordered_multimap::key_eq

Non-member functions

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

std::swap

erase_if (C++20)

Deduction guides(C++17)

 

void reserve( size_type count );		(since C++11)

Sets the number of buckets to the number needed to accomodate at least count elements without exceeding maximum load factor and rehashes the container, i.e. puts the elements into appropriate buckets considering that total number of buckets has changed. Effectively calls rehash(std::ceil(count / max_load_factor())).

Parameters

count

-

new capacity of the container

Return value

(none)

Complexity

Average case linear in the size of the container, worst case quadratic.

See also

rehash (C++11)

reserves at least the specified number of buckets and regenerates the hash table (public member function)