# std::unordered_set<Key,Hash,KeyEqual,Allocator>::insert_range

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< cpp‎ | container‎ | unordered set

template< container-compatible-range <value_type> R > void insert_range( R&& rg ); |  | (since C++23)

Inserts a copy of each element in the range rg if and only if there is no element with key equivalent to the key of that element in *this.

Each iterator in the range rg is dereferenced exactly once. The behavior is undefined if rg overlaps with the container.

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.

### Parameters

rg | - | a container compatible range, that is, an `input_range` whose elements are convertible to `T`
Type requirements
- `value_type` must be EmplaceConstructible into `unordered_set` from * ranges::begin (rg). Otherwise, the behavior is undefined.

### Return value

(none)

### Complexity

Average case O(N), where N is ranges::distance (rg), worst case O(N·(a.size() + 1)).

### Notes

Feature-test macro | Value | Std | Feature
--- | --- | --- | ---
`__cpp_lib_containers_ranges` | `202202L` | (C++23) | Ranges-aware construction and insertion

### Example

Run this code

    #include <iostream>
    #include <unordered_set>

    void println(auto, auto const& container)
    {
        for (const auto& elem : container)
            std::cout << elem << ' ';
        std::cout << '\n';
    }

    int main()
    {
        auto container = std::unordered_set{1, 3, 2, 4};
        const auto rg = {-1, 3, -2};
    #ifdef __cpp_lib_containers_ranges
        container.insert_range(rg);
    #else
        container.insert(rg.begin(), rg.end());
    #endif
        println("{}", container);
    }

Possible output:

    4 -1 2 3 -2 1

### See also

insert | inserts elements or nodes(since C++17) (public member function)

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