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

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< cpp‎ | container‎ | unordered set

bool empty() const noexcept; |  | (since C++11) (until C++20)
[[nodiscard]] bool empty() const noexcept; |  | (since C++20)

Checks if the container has no elements, i.e. whether begin() == end().

### Parameters

(none)

### Return value

true if the container is empty, false otherwise

### Complexity

Constant.

### Example

The following code uses `empty` to check if a std::unordered_set <int> contains any elements:

Run this code

    #include <unordered_set>
    #include <iostream>

    int main()
    {
        std::unordered_set<int> numbers;
        std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';

        numbers.insert(42);
        numbers.insert(13317);
        std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
    }

Output:

    Initially, numbers.empty(): 1
    After adding elements, numbers.empty(): 0

### See also

size | returns the number of elements (public member function)

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