std::unordered_multiset<Key,Hash,KeyEqual,Allocator>::find

From cppreference.com

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
Execution control library(C++26)
Technical specifications
Symbols index
External libraries

[edit]

Containers library

node-handle (C++17)
Sequence
array (C++11)
vector
vector<bool>
inplace_vector (C++26)
hive (C++26)
deque
forward_list (C++11)
list
Associative
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
flat_set (C++23)
flat_multiset (C++23)
flat_map (C++23)
flat_multimap (C++23)
Views
span (C++20)
mdspan (C++23)
Tables
Iterator invalidation
Member function table
Non-member function table

[edit]

std::unordered_multiset

Member types

Member functions

unordered_multiset::unordered_multiset
unordered_multiset::~unordered_multiset
unordered_multiset::operator=
unordered_multiset::get_allocator
Iterators
unordered_multiset::beginunordered_multiset::cbegin
unordered_multiset::endunordered_multiset::cend
Capacity
unordered_multiset::size
unordered_multiset::max_size
unordered_multiset::empty
Modifiers
unordered_multiset::clear
unordered_multiset::insert
unordered_multiset::insert_range (C++23)
unordered_multiset::emplace
unordered_multiset::emplace_hint
unordered_multiset::erase
unordered_multiset::swap
unordered_multiset::extract (C++17)
unordered_multiset::merge (C++17)

Lookup
unordered_multiset::count
unordered_multiset::find
unordered_multiset::contains (C++20)
unordered_multiset::equal_range
Bucket interface
unordered_multiset::begin(size_type)unordered_multiset::cbegin(size_type)
unordered_multiset::end(size_type)unordered_multiset::cend(size_type)
unordered_multiset::bucket_count
unordered_multiset::max_bucket_count
unordered_multiset::bucket_size
unordered_multiset::bucket
Hash policy
unordered_multiset::load_factor
unordered_multiset::max_load_factor
unordered_multiset::rehash
unordered_multiset::reserve
Observers
unordered_multiset::hash_function
unordered_multiset::key_eq

Non-member functions

operator==operator!=

(until C++20)

std::swap(std::unordered_multiset)
erase_if(std::unordered_multiset) (C++20)

Deduction guides(C++17)

[edit]

iterator find(const Key& key);	(1)	(since C++11) (constexpr since C++26)
const_iterator find(const Key& key)const;	(2)	(since C++11) (constexpr since C++26)
template<class K> iterator find(const K& x);	(3)	(since C++20) (constexpr since C++26)
template<class K> const_iterator find(const K& x)const;	(4)	(since C++20) (constexpr since C++26)

1,2) Finds an element with key equivalent tokey.If there are several elements with the requested key in the container, any of them may be returned.

3,4) Finds an element with key that compares equivalent tox.

This overload participates in overload resolution only ifHash andKeyEqual are bothtransparent. This assumes that suchHash is callable with bothK andKey type, and that theKeyEqual is transparent, which, together, allows calling this function without constructing an instance ofKey.

[edit]Parameters

key	-	key value of the element to search for
x	-	a value of any type that can be transparently compared with a key

[edit]Return value

An iterator to the requested element. If no such element is found, past-the-end (seeend()) iterator is returned.

[edit]Complexity

Constant on average, worst case linear in the size of the container.

Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_generic_unordered_lookup`	`201811L`	(C++20)	Heterogeneous comparison lookup inunordered associative containers; overloads(3,4)

[edit]Example

Run this code

#include <iostream>#include <unordered_set> int main(){// Simple comparison demo.std::unordered_multiset<int> example{1,2,3,4}; if(auto search= example.find(2); search!= example.end())std::cout<<"Found "<<(*search)<<'\n';elsestd::cout<<"Not found\n";}

Output:

Found 2

[edit]See also

count	returns the number of elements matching specific key (public member function)[edit]
equal_range	returns range of elements matching a specific key (public member function)[edit]