std::vector<T,Allocator>:: size

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C++
Containers library
std::vector
Member types
Member functions
Non-member functions
(until C++20) (until C++20) (until C++20) (until C++20) (until C++20)
Deduction guides (C++17)
size_type size ( ) const ;
(noexcept since C++11)
(constexpr since C++20)

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:: vector < int > :

Run this code 
#include <cassert>
#include <vector>
 
int main()
{
    std::vector<int> nums;
    assert(nums.size() == 0);
    nums = {1, 2, 3, 4};
    assert(nums.size() == 4);
}

See also

returns the number of elements that can be held in currently allocated storage
(public member function)
checks whether the container is empty
(public member function)
returns the maximum possible number of elements
(public member function)
changes the number of elements stored
(public member function)
(C++17) (C++20)
returns the size of a container or array
(function template)
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