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

 

C++

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Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (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

 

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::size multiset::max_size multiset::empty Observers multiset::key_comp multiset::value_comp Modifiers multiset::clear multiset::erase multiset::swap multiset::extract (C++17) multiset::merge (C++17) multiset::insert multiset::insert_range (C++23) multiset::emplace (C++11) multiset::emplace_hint (C++11) Lookup multiset::count multiset::find multiset::contains (C++20) multiset::equal_range multiset::lower_bound multiset::upper_bound

Non-member functions

std::swap(std::multiset) erase_if(std::multiset) (C++20)   operator==operator<=> (C++20) operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)

Deduction guides(C++17)

 

	(1)
iterator erase( iterator pos );			(until C++23)
iterator erase( iterator pos )     requires(!std::same_as<iterator, const_iterator>);			(since C++23)
iterator erase( const_iterator pos );		(2)	(since C++11)
		(3)
iterator erase( iterator first, iterator last );				(until C++11)
iterator erase( const_iterator first, const_iterator last );				(since C++11)
size_type erase( const Key& key );			(4)
template< class K > size_type erase( K&& x );			(5)	(since C++23)

Removes specified elements from the container. The order of the remaining equivalent elements is preserved.

1,2) Removes the element at pos. Only one overload is provided if iterator and const_iterator are the same type.(since C++11)

3) Removes the elements in the range [first, last), which must be a valid range in *this.

4) Removes all elements with the key equivalent to key.

5) Removes all elements with key that compares equivalent to the value x. This overload participates in overload resolution only if the qualified-id Compare::is_transparent is valid and denotes a type, and neither iterator nor const_iterator is implicitly convertible from K. It allows calling this function without constructing an instance of Key.

References and iterators to the erased elements are invalidated. Other references and iterators are not affected.

The iterator pos must be valid and dereferenceable. Thus the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos.

Parameters

pos	-	iterator to the element to remove
first, last	-	range of elements to remove
key	-	key value of the elements to remove
x	-	a value of any type that can be transparently compared with a key denoting the elements to remove

Return value

1-3) Iterator following the last removed element.

4) Number of elements removed.

5) Number of elements removed.

Exceptions

1-3) Throws nothing.

4,5) Any exceptions thrown by the Compare object.

Complexity

Given an instance c of multiset:

1,2) Amortized constant

3) log(c.size()) + std::distance(first, last)

4) log(c.size()) + c.count(key)

5) log(c.size()) + c.count(x)

Notes

Feature-test macro	Value	Std	Feature
__cpp_lib_associative_heterogeneous_erasure	202110L	(C++23)	Heterogeneous erasure in associative containers and unordered associative containers; overload (5)

Example

Run this code

#include <set>
#include <iostream>
 
int main()
{
    std::multiset<int> c = {1, 2, 3, 4, 1, 2, 3, 4};
 
    auto print = [&c]
    {
        std::cout << "c = { ";
        for (int n : c)
            std::cout << n << ' ';
        std::cout << "}\n";
    };
    print();
 
    std::cout << "Erase all odd numbers:\n";
    for (auto it = c.begin(); it != c.end();)
    {
        if (*it % 2 != 0)
            it = c.erase(it);
        else
            ++it;
    }
    print();
 
    std::cout << "Erase 1, erased count: " << c.erase(1) << '\n';
    std::cout << "Erase 2, erased count: " << c.erase(2) << '\n';
    std::cout << "Erase 2, erased count: " << c.erase(2) << '\n';
    print();
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 130	C++98	the return type of overloads (1) and (3) was void (it is not consistent with the erase() requirement on sequence containers)	corrected to iterator
LWG 371	C++98	the order of equivalent elements that are not erased was not guaranteed to be preserved	required to be preserved
LWG 2059	C++11	replacing overload (1) with overload (2) introduced new ambiguity	added overload (1) back

See also

clear

clears the contents (public member function)