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std::unordered_map reserve() method

// Const version only
void reserve( size_type count );

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 - O(size())
Worst case, quadratic in the size of the container - O(size() * size()).

Exceptions​

(none)

Examples​

important

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std::unordered_map reserve() method

// Const version only
void reserve( size_type count );

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 - O(size())
Worst case, quadratic in the size of the container - O(size() * size()).

Exceptions​

(none)

Examples​

important

This section requires improvement. You can help by editing this doc page.

This article originates from this CppReference page. It was likely altered for improvements or editors' preference. Click "Edit this page" to see all changes made to this document.
Hover to see the original license.