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

	(1)
multiset();		(until C++11)
multiset() : multiset(Compare()) { }		(since C++11)
explicit multiset( const Compare& comp, const Allocator& alloc = Allocator() );	(2)
explicit multiset( const Allocator& alloc );	(3)	(since C++11)
template< class InputIt > multiset( InputIt first, InputIt last, const Compare& comp = Compare(), const Allocator& alloc = Allocator() );	(4)
template< class InputIt > multiset( InputIt first, InputIt last, const Allocator& alloc ) : multiset(first, last, Compare(), alloc) { }	(5)	(since C++14)
multiset( const multiset& other );	(6)
multiset( const multiset& other, const Allocator& alloc );	(7)	(since C++11)
multiset( multiset&& other );	(8)	(since C++11)
multiset( multiset&& other, const Allocator& alloc );	(9)	(since C++11)
multiset( std::initializer_list<value_type> init, const Compare& comp = Compare(), const Allocator& alloc = Allocator() );	(10)	(since C++11)
multiset( std::initializer_list<value_type> init, const Allocator& alloc ) : multiset(init, Compare(), alloc) { }	(11)	(since C++14)
template< container-compatible-range<value_type> R > multiset( std::from_range_t, R&& rg, const Compare& comp = Compare(), const Allocator& alloc = Allocator() );	(12)	(since C++23)
template< container-compatible-range<value_type> R > multiset( std::from_range_t, R&& rg, const Allocator& alloc ) : multiset(std::from_range, std::forward<R>(rg), Compare(), alloc) { }	(13)	(since C++23)

Constructs new container from a variety of data sources and optionally using user supplied allocator alloc or comparison function object comp.

1-3) Constructs an empty container.

4-5) Constructs the container with the contents of the range [first, last).

6-7) Copy constructor. Constructs the container with the copy of the contents of other.

If `alloc` is not provided, allocator is obtained by calling `std::allocator_traits<allocator_type>:: select_on_container_copy_construction(other.get_allocator())`.	(since C++11)
During class template argument deduction, only the first argument contributes to the deduction of the container's `Allocator` template parameter.	(since C++23)

8-9) Move constructor. Constructs the container with the contents of other using move semantics. If alloc is not provided, allocator is obtained by move-construction from the allocator belonging to other.

During class template argument deduction, only the first argument contributes to the deduction of the container's Allocator template parameter.

(since C++23)

10-11) Initializer-list constructor. Constructs the container with the contents of the initializer list init.

12-13) Constructs the container with the contents of rg.

Parameters

alloc	-	allocator to use for all memory allocations of this container
comp	-	comparison function object to use for all comparisons of keys
first, last	-	the range `[first,` `last)` to copy the elements from
rg	-	a container compatible range, that is, an `input_range` whose elements are convertible to `value_type`
other	-	another container to be used as source to initialize the elements of the container with
init	-	initializer list to initialize the elements of the container with
Type requirements
-`InputIt` must meet the requirements of LegacyInputIterator.
-`Compare` must meet the requirements of Compare.
-`Allocator` must meet the requirements of Allocator.

Complexity

1-3) Constant.

4-5) N·log(N) where N = std::distance(first, last) in general, linear in N if the range is already sorted by value_comp().

6-7) Linear in size of other.

8-9) Constant. If alloc is given and alloc != other.get_allocator(), then linear.

10-11) N·log(N) where N = init.size() in general, linear in N if init is already sorted by value_comp().

12-13) N·log(N) where N = ranges::distance(rg) in general, linear in N if the range is already sorted by value_comp().

Exceptions

Calls to Allocator::allocate may throw.

Notes

After container move construction (overload (8-9)), references, pointers, and iterators (other than the end iterator) to other remain valid, but refer to elements that are now in *this. The current standard makes this guarantee via the blanket statement in [container.rev.reqmts]/17, and a more direct guarantee is under consideration via LWG 2321.

Although not formally required until C++23, some implementations has already put the template parameter Allocator into non-deduced contexts in earlier modes.

Feature-test macro	Value	Std	Comment
`__cpp_lib_containers_ranges`	202202L	(C++23)	Ranges-aware construction and insertion; overloads (12,13)

Example

#include <iostream>
#include <set>
#include <string_view>
 
void print(const std::string_view name, const std::multiset<int>& ms)
{
    std::cout << name << ": ";
    for (auto element : ms)
        std::cout << element << ' ';
    std::cout << '\n';
}
 
int main()
{
    // (1) Default constructor
    std::multiset<int> a;
    a.insert(4);
    a.insert(3);
    a.insert(2);
    a.insert(1);
    print("a", a);
 
    // (4) Iterator constructor
    std::multiset<int> b(a.begin(), a.find(3));
    print("b", b);
 
    // (6) Copy constructor
    std::multiset<int> c(a);
    print("c", c);
 
    // (8) Move constructor
    std::multiset<int> d(std::move(a));
    print("d", d);
 
    // (10) Initializer list constructor
    std::multiset<int> e{3, 2, 1, 2, 4, 7, 3};
    print("e", e);
}

Output:

a: 1 2 3 4
b: 1 2
c: 1 2 3 4
d: 1 2 3 4
e: 1 2 2 3 3 4 7

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 2193	C++11	the default constructor is explicit	made non-explicit