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

void clear();		(until C++11)
void clear() noexcept;		(since C++11)

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

Invalidates any references, pointers, or iterators referring to contained elements. Any past-the-end iterator remains valid.

Parameters

(none)

Return value

(none)

Complexity

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

Example

Run this code

#include <algorithm>
#include <iostream>
#include <set>
 
int main()
{
    std::multiset<int> container{1, 2, 3};
 
    auto print = [](const int& n) { std::cout << ' ' << n; };
 
    std::cout << "Before clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << '\n';
 
    std::cout << "Clear\n";
    container.clear();
 
    std::cout << "After clear:";
    std::for_each(container.begin(), container.end(), print);
    std::cout << "\nSize=" << container.size() << '\n';
}

Output:

Before clear: 1 2 3
Size=3
Clear
After clear:
Size=0

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 224	C++98	the complexity was log(size()) + N, but N was not defined	corrected to 'linear in size()'

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multiset::multiset
multiset::~multiset
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multiset::beginmultiset::cbegin (C++11)
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multiset::rbeginmultiset::crbegin (C++11)
multiset::rendmultiset::crend (C++11)
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multiset::clear
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multiset::erase
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operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
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