std::unordered_multiset emplace() method

since C++11

// Non const version only
template< class... Args >
std::pair<iterator,bool> emplace( Args&&... args );

Inserts a new element into the container constructed in-place with the given args if there is no element with the key in the container.

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

Careful use of emplace allows the new element to be constructed while avoiding unnecessary copy or move operations. The constructor of the new element is called with exactly the same arguments as supplied to emplace, forwarded via std::forward<Args>(args)....

Invalidation

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().

Parameters

• args - arguments to forward to the constructor of the element

Return value

Returns an iterator to the inserted element.

Complexity

Average case, amortized constant - O(1).
Worst case, linear in size of the container - O(size()).

Exceptions

If an exception is thrown by any operation, this function has no effect (strong exception guarantee).

Example

important

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