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

 

C++

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External libraries

 

Containers library

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array (C++11)

vector

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forward_list (C++11)

list

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unordered_set (C++11)

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unordered_map (C++11)

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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

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unordered_set::erase

unordered_set::swap

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unordered_set::merge (C++17)

Lookup

unordered_set::count

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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

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)