std::flat_multimap<Key,T,Compare,KeyContainer,MappedContainer>::clear

 

C++

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Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

Containers library

node-handle (C++17)

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array (C++11)

vector

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list

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unordered_set (C++11)

unordered_multiset (C++11)

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unordered_multimap (C++11)

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stack

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flat_map (C++23)

flat_multimap (C++23)

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std::flat_multimap

Member types

Member functions

flat_multimap::flat_multimap    flat_multimap::operator= Modifiers flat_multimap::clear flat_multimap::erase flat_multimap::swap flat_multimap::extract flat_multimap::replace flat_multimap::insert flat_multimap::insert_range flat_multimap::emplace flat_multimap::emplace_hint Lookup flat_multimap::count flat_multimap::find flat_multimap::contains flat_multimap::equal_range flat_multimap::lower_bound flat_multimap::upper_bound Iterators flat_multimap::beginflat_multimap::cbegin flat_multimap::endflat_multimap::cend flat_multimap::rbeginflat_multimap::crbegin flat_multimap::rendflat_multimap::crend Capacity flat_multimap::size flat_multimap::max_size flat_multimap::empty Observers flat_multimap::key_comp flat_multimap::keys flat_multimap::value_comp flat_multimap::values

Non-member functions

swap(std::flat_multimap) erase_if(std::flat_multimap)     operator==operator<=>

Helper classes

uses_allocator<std::flat_multimap>

Tags

sorted_equivalent          sorted_equivalent_t

Deduction guides

 

void clear() noexcept;		(since C++23) (constexpr since C++26)

Erases all elements from the container adaptor. After this call, size() returns zero.

Invalidates any references, pointers, and iterators referring to contained elements.

Complexity

Linear in the size of the container adaptor, i.e., the number of elements.

Example

Run this code

#include <iostream>
#include <string_view>
#include <flat_map>
 
void print_info(std::string_view rem, const std::flat_multimap<int, char>& v)
{
    std::cout << rem << "{ ";
    for (const auto& [key, value] : v)
        std::cout << '[' << key << "]:" << value << ' ';
    std::cout << "}\n";
    std::cout << "Size=" << v.size() << '\n';
}
 
int main()
{
    std::flat_multimap<int, char> container{{1, 'x'}, {2, 'y'}, {3, 'z'};
    print_info("Before clear: ", container);
    container.clear();
    print_info("After clear: ", container);
}

Output:

Before clear: { [1]:x [2]:y [3]:z }
Size=3
After clear: { }
Size=0

See also

erase

erases elements (public member function)

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