size_type size() const;  |  (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.
Exceptions
noexcept specification: noexceptComplexity
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
|  checks whether the container is empty  (public member function)  |  |
|  returns the maximum possible number of elements  (public member function)  |  
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