std::map::size

size_type size() const;

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

(none)	(until C++11)
`noexcept` specification: `noexcept`	(since C++11)

Complexity

Constant.

Example

The following code uses size to display the number of elements in a std::map:

#include <map>
#include <iostream>
 
int main()
{ 
    std::map<int,char> nums {{1, 'a'}, {3, 'b'}, {5, 'c'}, {7, 'd'}};
 
    std::cout << "nums contains " << nums.size() << " elements.\n";
}

Output:

nums contains 4 elements.

empty	checks whether the container is empty (public member function)
max_size	returns the maximum possible number of elements (public member function)