std::map<Key,T,Compare,Allocator>::erase

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std::map

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map::map
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operator==operator<=> (C++20)
std::swap(std::map)
erase_if(std::map) (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)

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iterator erase( iterator pos);	(1)	(constexpr since C++26)
iterator erase( const_iterator pos);	(2)	(since C++11) (constexpr since C++26)
	(3)
iterator erase( iterator first, iterator last);			(until C++11)
iterator erase( const_iterator first, const_iterator last);			(since C++11) (constexpr since C++26)
size_type erase(const Key& key);		(4)	(constexpr since C++26)
template<class K> size_type erase( K&& x);		(5)	(since C++23) (constexpr since C++26)

Removes specified elements from the container.

1,2) Removes the element atpos.

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

4) Removes the element (if one exists) with the key equivalent tokey.

5) Removes all elements with key that compares equivalent to the valuex.

This overload participates in overload resolution only ifCompare istransparent, and neitheriterator norconst_iterator is implicitly convertible fromK. It allows calling this function without constructing an instance ofKey.

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

The iteratorpos must be dereferenceable. Thus theend() iterator (which is valid, but is not dereferenceable) cannot be used as a value forpos.

[edit]Parameters

pos	-	iterator to the element to remove
first, last	-	the pair of iterators defining therange 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

[edit]Return value

1-3) Iterator following the last removed element.

4) Number of elements removed (0 or 1).

5) Number of elements removed.

[edit]Exceptions

1-3) Throws nothing.

4,5) Any exceptions thrown by theCompare object.

[edit]Complexity

Given an instancec ofmap:

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 inassociative containers andunordered associative containers; overload(5)

[edit]Example

Run this code

#include <map>#include <iostream> int main(){std::map<int,std::string> c={{1,"one"},{2,"two"},{3,"three"},{4,"four"},{5,"five"},{6,"six"}}; // erase all odd numbers from cfor(auto it= c.begin(); it!= c.end();){if(it->first%2!=0)            it= c.erase(it);else++it;} for(auto& p: c)std::cout<< p.second<<' ';std::cout<<'\n';}

Output:

two four six

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) wasvoid (it is not consistent with the`erase()` requirement on sequence containers)	corrected to`iterator`
LWG 2059	C++11	replacing overload(1) with overload(2) introduced new ambiguity	added overload(1) back