std::multiset<Key,Compare,Allocator>::find

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

map

multimap

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

stack

queue

priority_queue

span (C++20)

 

std::multiset

Member functions

multiset::multiset

multiset::~multiset

multiset::operator=

multiset::get_allocator

Iterators

multiset::beginmultiset::cbegin (C++11)

multiset::endmultiset::cend (C++11)

multiset::rbeginmultiset::crbegin (C++11)

multiset::rendmultiset::crend (C++11)

Capacity

multiset::empty

multiset::size

multiset::max_size

Modifiers

multiset::clear

multiset::insert

multiset::emplace (C++11)

multiset::emplace_hint (C++11)

multiset::erase

multiset::swap

multiset::extract (C++17)

multiset::merge (C++17)

Lookup

multiset::count

multiset::find

multiset::contains (C++20)

multiset::equal_range

multiset::lower_bound

multiset::upper_bound

Observers

multiset::key_comp

multiset::value_comp

Deduction guides(C++17)

 

iterator find( const Key& key );	(1)
const_iterator find( const Key& key ) const;	(2)
template< class K > iterator find( const K& x );	(3)	(since C++14)
template< class K > const_iterator find( const K& x ) const;	(4)	(since C++14)

1,2) Finds an element with key equivalent to key.

3,4) Finds an element with key that compares equivalent to the value x. This overload only participates in overload resolution if the qualified-id Compare::is_transparent is valid and denotes a type. It allows calling this function without constructing an instance of Key

Parameters

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

Return value

Iterator to an element with key equivalent to key. If no such element is found, past-the-end (see end()) iterator is returned.

Complexity

Logarithmic in the size of the container.

Example

Run this code

#include <iostream>
#include <set>
struct FatKey   { int x; int data[1000]; };
struct LightKey { int x; };
bool operator<(const FatKey& fk, const LightKey& lk) { return fk.x < lk.x; }
bool operator<(const LightKey& lk, const FatKey& fk) { return lk.x < fk.x; }
bool operator<(const FatKey& fk1, const FatKey& fk2) { return fk1.x < fk2.x; }
int main()
{  
// simple comparison demo
    std::multiset<int> example = {1, 2, 3, 4};
 
    auto search = example.find(2);
    if (search != example.end()) {
        std::cout << "Found " << (*search) << '\n';
    } else {
        std::cout << "Not found\n";
    }
 
// transparent comparison demo
    std::multiset<FatKey, std::less<>> example2 = { {1, {} }, {2, {} }, {3, {} }, {4, {} } };
 
    LightKey lk = {2};
    auto search2 = example2.find(lk);
    if (search2 != example2.end()) {
        std::cout << "Found " << search2->x << '\n';
    } else {
        std::cout << "Not found\n";
    }
}

Output:

Found 2
Found 2

See also

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