NAME¶

std::multimap::insert - std::multimap::insert

Synopsis¶

iterator insert( const value_type& value ); (1)
iterator insert( value_type&& value ); (2) (since C++17)
template< class P > (3) (since C++11)
iterator insert( P&& value );
iterator insert( iterator pos, const value_type& (until C++11)
value );
iterator insert( const_iterator pos, const (since C++11)
value_type& value );
iterator insert( const_iterator pos, value_type&& (5) (since C++17)
value );
template< class P > (6) (since C++11)
iterator insert( const_iterator pos, P&& value ); (4)
template< class InputIt > (7)
void insert( InputIt first, InputIt last );
void insert( std::initializer_list<value_type> ilist (8) (since C++11)
);
iterator insert( node_type&& nh ); (9) (since C++17)
iterator insert( const_iterator pos, node_type&& nh (10) (since C++17)
);

Inserts element(s) into the container.

1-3) Inserts value. If the container has elements with equivalent key, inserts at
the upper bound of that range.
Overload (3) is equivalent to emplace(std::forward<P>(value)) and only participates
in overload resolution if std::is_constructible<value_type, P&&>::value == true.
4-6) Inserts value in the position as close as possible to the position just prior
to pos.
Overload (6) is equivalent to emplace_hint(hint, std::forward<P>(value)) and only
participates in overload resolution if std::is_constructible<value_type, P&&>::value
== true.
7) Inserts elements from range [first, last).
8) Inserts elements from initializer list ilist.
9) If nh is an empty node handle, does nothing. Otherwise, inserts the element owned
by nh into the container and returns an iterator pointing at the inserted element.
If a range containing elements with keys equivalent to nh.key() exists in the
container, the element is inserted at the end of that range. The behavior is
undefined if nh is not empty and get_allocator() != nh.get_allocator().
10) If nh is an empty node handle, does nothing and returns the end iterator.
Otherwise, inserts the element owned by nh into the container, and returns the
iterator pointing to the element with key equivalent to nh.key(). The element is
inserted as close as possible to the position just prior to pos. The behavior is
undefined if nh is not empty and get_allocator() != nh.get_allocator().

No iterators or references are invalidated.
If the insertion is successful, pointers and references to the element obtained
while it is held in the node handle are invalidated, and pointers and references
obtained to that element before it was extracted become valid.
(since C++17)

Parameters¶

pos - iterator to the position before which the new element will be inserted
value - element value to insert
first, last - range of elements to insert
ilist - initializer list to insert the values from
nh - a compatible node handle

Type requirements¶

-
InputIt must meet the requirements of LegacyInputIterator.

Return value¶

1-6) An iterator to the inserted element.
7,8) (none)
9,10) End iterator if nh was empty, iterator pointing to the inserted element
otherwise.

Exceptions¶

1-6) If an exception is thrown by any operation, the insertion has no effect.
7,8) No exception safety guarantee.
9,10) If an exception is thrown by any operation, the insertion has no effect.

Complexity¶

1-3) O(log(size()))
4-6) Amortized constant if the insertion happens in the position just before pos,
O(log(size())) otherwise.
7,8) O(N·log(size() + N)), where N is the number of elements to insert.
9) O(log(size()))
10) Amortized constant if the insertion happens in the position just before pos,
O(log(size())) otherwise.

Example¶

// Run this code

#include <functional>
#include <iostream>
#include <map>
#include <string>
#include <string_view>
#include <utility>

template<class M>
void print(const std::string_view rem, const M& mmap)
{
std::cout << rem << ' ';
for (const auto& e : mmap)
std::cout << '{' << e.first << ',' << e.second << "} ";
std::cout << '\n';
}

int main()
{
// list-initialize
std::multimap<int, std::string, std::greater<int>> mmap
{{2, "foo"}, {2, "bar"}, {3, "baz"}, {1, "abc"}, {5, "def"}};
print("#1", mmap);

// insert using value_type
mmap.insert(decltype(mmap)::value_type(5, "pqr"));
print("#2", mmap);

// insert using pair
mmap.insert(std::pair{6, "uvw"});
print("#3", mmap);

mmap.insert({7, "xyz"});
print("#4", mmap);

// insert using initializer_list
mmap.insert({{5, "one"}, {5, "two"}});
print("#5", mmap);

// insert using a pair of iterators
mmap.clear();
const auto il = {std::pair{1, "ä"}, {2, "ё"}, {2, "ö"}, {3, "ü"}};
mmap.insert(il.begin(), il.end());
print("#6", mmap);
}

Output:¶

#1 {5,def} {3,baz} {2,foo} {2,bar} {1,abc}
#2 {5,def} {5,pqr} {3,baz} {2,foo} {2,bar} {1,abc}
#3 {6,uvw} {5,def} {5,pqr} {3,baz} {2,foo} {2,bar} {1,abc}
#4 {7,xyz} {6,uvw} {5,def} {5,pqr} {3,baz} {2,foo} {2,bar} {1,abc}
#5 {7,xyz} {6,uvw} {5,def} {5,pqr} {5,one} {5,two} {3,baz} {2,foo} {2,bar} {1,abc}
#6 {3,ü} {2,ё} {2,ö} {1,ä}

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
the insertion is required
pos was just a hint, it could be to
LWG 233 C++98 totally ignored be as close as possible to
the
position just prior to pos
the complexity of overload (5) was removed the linear
LWG 264 C++98 required to be linear if requirement
the range [first, last) is sorted in this special case
according to Compare
LWG 371 C++98 the order of equivalent elements required to be preserved
was not guaranteed to be preserved
LWG 2005 C++11 overloads (3,6) were poorly described improved the description

See also¶

emplace constructs element in-place
(C++11) (public member function)
emplace_hint constructs elements in-place using a hint
(C++11) (public member function)
inserter creates a std::insert_iterator of type inferred from the argument
(function template)