# std::unordered_map<Key,T,Hash,KeyEqual,Allocator>::reserve

From cppreference.com
< cpp‎ | container‎ | unordered map

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

Sets the number of buckets to the number needed to accommodate 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)

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