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| Associative | ||||
| Unordered associative | ||||
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| Iterator invalidation | ||||
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| Non-member function table |
std::unordered_set| Member types | ||||||
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| Deduction guides(C++17) | ||||||
template<class...Args> std::pair<iterator,bool> emplace( Args&&...args); | (since C++11) (constexpr since C++26) | |
Inserts a new element into the container constructed in-place with the givenargs, if there is no element with the key in the container.
The constructor of the new element is called with exactly the same arguments as supplied toemplace, forwarded viastd::forward<Args>(args)....The element may be constructed even if there already is an element with the key in the container, in which case the newly constructed element will be destroyed immediately .
Ifvalue_type is notEmplaceConstructible intounordered_set fromargs, the behavior is undefined.
If after the operation the new number of elements is greater than oldmax_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 |
| args | - | arguments to forward to the constructor of the element |
A pair consisting of an iterator to the inserted element (or to the element that prevented the insertion) and abool value set totrue if and only if the insertion took place.
If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).
Amortized constant on average, worst case linear in the size of the container.
Careful use ofemplace allows the new element to be constructed while avoiding unnecessary copy or move operations.
| This section is incomplete Reason: no example |
| constructs elements in-place using a hint (public member function)[edit] | |
| inserts elementsor nodes(since C++17) (public member function)[edit] |
