std::map::size

 

C++

Language

Standard library headers

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Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Containers library

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std::map

Member functions

map::map

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Element access

map::at

map::operator[]

Iterators

map::begin map::cbegin (C++11)

map::end map::cend (C++11)

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Capacity

map::empty

map::size

map::max_size

Modifiers

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Lookup

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Observers

map::key_comp

map::value_comp

 

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

noexcept specification:  

noexcept

  (since C++11)

Complexity

Constant.

Example

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

run this code

#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.

See also

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