cpp / latest / container / unordered_set / size.html /

std::unordered_set<Key,Hash,KeyEqual,Allocator>::size

size_type size() const noexcept;
(since C++11)

Returns the number of elements in the container, i.e. std::distance(begin(), end()).

Parameters

(none).

Return value

The number of elements in the container.

Complexity

Constant.

Example

The following code uses size to display the number of elements in a std::unordered_set<int>:

#include <unordered_set>
#include <iostream>
 
int main()
{ 
    std::unordered_set<int> nums {1, 3, 5, 7};
 
    std::cout << "nums contains " << nums.size() << " elements.\n";
}

Output:

nums contains 4 elements.

See also

(C++11)
checks whether the container is empty
(public member function)
(C++11)
returns the maximum possible number of elements
(public member function)
(C++17)(C++20)
returns the size of a container or array
(function template)

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/container/unordered_set/size