# std::unordered_multiset<Key,Hash,KeyEqual,Allocator>::insert

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< cpp‎ | container‎ | unordered multiset

iterator insert( const value_type& value ); | (1) | (since C++11)
iterator insert( value_type&& value ); | (2) | (since C++11)
iterator insert( const_iterator hint, const value_type& value ); | (3) | (since C++11)
iterator insert( const_iterator hint, value_type&& value ); | (4) | (since C++11)
template< class InputIt > void insert( InputIt first, InputIt last ); | (5) | (since C++11)
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`.
3-4) Inserts `value`, using `hint` as a non-binding suggestion to where the search should start.
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.. 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 `hint`. The behavior is undefined if `nh` is not empty and get_allocator() != nh.get_allocator().

If rehashing occurs due to the insertion, all iterators are invalidated. Otherwise iterators are not affected. References are not invalidated. Rehashing occurs only if the new number of elements is greater than max_load_factor()*bucket_count(). 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 insert the content
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

1-4) Average case: `O(1)`, worst case `O(size())`
5-6) Average case: `O(N)`, where N is the number of elements to insert. Worse case: `O(N*size()+N)`
7-8) Average case: `O(1)`, worst case `O(size())`

### See also

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

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