std::unordered_multimap<Key,T,Hash,KeyEqual,Allocator>::emplace - cppreference.com (original) (raw)

| template< class... Args >iterator emplace( Args&&... args ); | | (since C++11) (constexpr since C++26) | | ------------------------------------------------------------- | | ------------------------------------- |

Inserts a new element into the container constructed in-place with the given args.

The constructor of the new element (i.e. std::pair<const Key, T>) is called with exactly the same arguments as supplied to emplace, forwarded via std::forward<Args>(args)....

If value_type is not EmplaceConstructible into unordered_multimap from args, the behavior is undefined.

If after the operation the new number of elements is greater than old max_load_factor() * bucket_count() a rehashing takes place.
If rehashing occurs (due to the insertion), all iterators are invalidated. Otherwise (no rehashing), iterators are not invalidated.

Contents

• 1 Parameters
• 2 Return value
• 3 Exceptions
• 4 Complexity
• 5 Notes
• 6 Example
• 7 See also

[edit] Parameters

[edit] Return value

An iterator to the inserted element.

[edit] Exceptions

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).

[edit] Complexity

Amortized constant on average, worst case linear in the size of the container.

[edit] Notes

Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations.

[edit] Example

Possible output:

a => a b => abcd c => cccccccccc d => ddd d => DDD

[edit] See also

| | constructs elements in-place using a hint (public member function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | inserts elements or nodes(since C++17) (public member function) [edit] |