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

 

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std::unordered_map

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unordered_map::unordered_map unordered_map::~unordered_map unordered_map::operator= unordered_map::get_allocator Iterators unordered_map::beginunordered_map::cbegin unordered_map::endunordered_map::cend Capacity unordered_map::size unordered_map::max_size unordered_map::empty Modifiers unordered_map::clear unordered_map::erase unordered_map::swap unordered_map::extract (C++17) unordered_map::merge (C++17) unordered_map::insert unordered_map::insert_range (C++23) unordered_map::insert_or_assign (C++17)   unordered_map::emplace unordered_map::emplace_hint unordered_map::try_emplace (C++17)	Lookup unordered_map::at unordered_map::operator[] unordered_map::count unordered_map::find unordered_map::contains (C++20) unordered_map::equal_range Bucket interface unordered_map::begin(size_type)unordered_map::cbegin(size_type) unordered_map::end(size_type)unordered_map::cend(size_type) unordered_map::bucket_count unordered_map::max_bucket_count unordered_map::bucket_size unordered_map::bucket Hash policy unordered_map::load_factor unordered_map::max_load_factor unordered_map::rehash unordered_map::reserve Observers unordered_map::hash_function unordered_map::key_eq
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operator==operator!= (until C++20)	std::swap(std::unordered_map) erase_if(std::unordered_map) (C++20)
Deduction guides(C++17)

 

size_type max_size()constnoexcept;		(since C++11) (constexpr since C++26)

Returns the maximum number of elements the container is able to hold due to system or library implementation limitations, i.e. std::distance(begin(), end()) for the largest container.

Return value

Maximum number of elements.

Complexity

Constant.

Notes

This value typically reflects the theoretical limit on the size of the container, at most std::numeric_limits<difference_type>::max(). At runtime, the size of the container may be limited to a value smaller than max_size() by the amount of RAM available.

Example

Run this code

#include <iostream>#include <locale>#include <unordered_map>   int main(){std::unordered_map<char, char> p;std::unordered_map<long, char> q;   std::cout.imbue(std::locale("en_US.UTF-8"));std::cout<<std::uppercase<<"p.max_size() = "<<std::dec<< p.max_size()<<" = 0x"<<std::hex<< p.max_size()<<'\n'<<"q.max_size() = "<<std::dec<< q.max_size()<<" = 0x"<<std::hex<< q.max_size()<<'\n';}

Possible output:

p.max_size() = 1,152,921,504,606,846,975 = 0xFFF,FFF,FFF,FFF,FFF q.max_size() = 768,614,336,404,564,650 = 0xAAA,AAA,AAA,AAA,AAA

See also

size	returns the number of elements (public member function)