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

From cppreference.com
< cpp‎ | container‎ | multiset
 
 
 
 
multiset();
(1)
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 );
(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& );
(11) (since C++14)

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)

The template parameter Allocator is only deduced from the first argument while used in class template argument deduction.

(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.

The template parameter Allocator is only deduced from the first argument while used in class template argument deduction.

(since C++23)
10-11) Constructs the container with the contents of the initializer list init.

Contents

[edit] 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 to copy the elements from
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.

[edit] 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().

[edit] Exceptions

Calls to Allocator::allocate may throw.

[edit] 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.requirements.general]/12, 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.

[edit] Example

#include <iostream>
#include <string_view>
#include <set>
 
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

[edit] 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

[edit] See also

assigns values to the container
(public member function) [edit]