std::multimap<Key,T,Compare,Allocator>::insert

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

Inserts element(s) into the container.

1-2) inserts value. If the container has elements with equivalent key, inserts at the upper bound of that range.(since C++11) The overload (2) is equivalent to emplace(std::forward<P>(value)) and only participates in overload resolution if std::is_constructible<value_type, P&&>::value == true.

3-4) inserts value in the position as close as possible, just prior(since C++11), to hint. The overload (4) 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.

5) inserts elements from range [first, last).

6) inserts elements from initializer list ilist.

7) 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().

8) 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 hint. 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

hint

iterator, used as a suggestion as to where to start the search	(until C++11)
iterator to the position before which the new element will be inserted	(since C++11)

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

1-4) Returns an iterator to the inserted element.

5-6) (none)

7,8) End iterator if nh was empty, iterator pointing to the inserted element otherwise.

Exceptions

1-4) If an exception is thrown by any operation, the insertion has no effect.

Complexity

1-2) Logarithmic in the size of the container, O(log(size())).

3-4) Amortized constant if the insertion happens in the position just after the hint, logarithmic in the size of the container otherwise.	(until C++11)
3-4) Amortized constant if the insertion happens in the position just before the hint, logarithmic in the size of the container otherwise.	(since C++11)

5-6) O(N*log(size() + N)), where N is the number of elements to insert.

7) Logarithmic in the size of the container, O(log(size())).

8) Amortized constant if the insertion happens in the position just before the hint, logarithmic in the size of the container otherwise.

Example

#include <iostream>
#include <string>
#include <map>
#include <functional>
 
template<class M>
void print(const M& mmap)
{
    for (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"}};
 
  // insert using value_type
  mmap.insert(decltype(mmap)::value_type(5, "pqr"));
  print(mmap);
 
  // insert using make_pair
  mmap.insert(std::make_pair(6, "uvw"));
  print(mmap);
 
  mmap.insert({7, "xyz"});
  print(mmap);
 
  // insert using initialization_list
  mmap.insert({{5, "one"}, {5, "two"}});
  print(mmap);
 
  // erase all entries with key 5
  mmap.erase(5);
  print(mmap);
 
  // find and erase a specific entry
  auto pos = mmap.begin();
  while (pos->second != "bar" && pos != mmap.end()) ++pos;
  mmap.erase(pos);
  print(mmap);
}

Output:

{5,def} {5,pqr} {3,baz} {2,foo} {2,bar} {1,abc} 
{6,uvw} {5,def} {5,pqr} {3,baz} {2,foo} {2,bar} {1,abc} 
{7,xyz} {6,uvw} {5,def} {5,pqr} {3,baz} {2,foo} {2,bar} {1,abc} 
{7,xyz} {6,uvw} {5,def} {5,pqr} {5,one} {5,two} {3,baz} {2,foo} {2,bar} {1,abc} 
{7,xyz} {6,uvw} {3,baz} {2,foo} {2,bar} {1,abc} 
{7,xyz} {6,uvw} {3,baz} {2,foo} {1,abc}

emplace (C++11)	constructs element in-place (public member function)
emplace_hint (C++11)	constructs elements in-place using a hint (public member function)