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

From cppreference.com
< cpp‎ | container‎ | multimap

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.

| This section is incomplete Reason: cases 5-6

### 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

Run this code

    #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}

### See also

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

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/container/multimap/insert&oldid=108443"