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std::multimap::erase(3) C++ Standard Libary std::multimap::erase(3) NAME std::multimap::erase - std::multimap::erase Synopsis iterator erase( iterator pos ); (1) iterator erase( const_iterator pos ); (2) (since C++11) iterator erase( iterator first, iterator last ); (until C++11) iterator erase( const_iterator first, const_iterator (since C++11) last ); (3) size_type erase( const Key& key ); (4) template< class K > (5) (since C++23) size_type erase( K&& x ); Removes specified elements from the container. The order of the re- maining equivalent elements is preserved. 1,2) Removes the element at pos. 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 it- erator 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 multimap: 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 Hetero- geneous erasure in associa- tive containers __cpp_lib_associative_heterogeneous_erasure 202110L (C++23) and un- ordered associa- tive containers; overload (5) Example // Run this code #include <map> #include <iostream> int main() { std::multimap<int, std::string> c = { {1, "one"}, {2, "two"}, {3, "three"}, {4, "four"}, {5, "five"}, {6, "six"} }; // erase all odd numbers from c for (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 retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior the return type of overloads (1) and (3) LWG 130 C++98 was void (it is not cor- rected to iterator consistent with the erase() requirement on sequence containers) the order of equivalent elements that LWG 371 C++98 are not re- quired to be erased was not guaranteed to be pre- served preserved LWG 2059 C++11 replacing overload (1) with overload (2) added overload (1) back introduced new ambiguity See also clear clears the contents (public member function) http://cppreference.com 2024.06.10 std::multimap::erase(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Complexity | Notes | Example | Output: | See also
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