array::size() in C++ STL

The array::size() method is used to find the number of elements in the array container. It is the member method std::array class defined inside <array> header file. In this article, we will learn about the array::size() method in C++.

Example:

// C++ Program to illustrate the use of array::size()
#include <bits/stdc++.h>
using namespace std;

int main() {
    array<int, 3> a = {1, 2, 3};

    cout << a.size();
    return 0;
}

3

array::size() Syntax

a.size();

Parameters

• This function does not require any parameter.

Return Value

• Returns the number of elements present in the array.
• If the array is empty, it returns 0.

Note: As std::arrays are fixed size containers whose size is set at the time of declaration, the array::size() method will always return the same size for the container instance.

More Examples of array::size()

The following examples demonstrates the use of array::size() function in different scenarios:

Example 1: Find the Size of Array of Strings

// C++ Program to find the size of array of
// strings using array::size()
#include <bits/stdc++.h>
using namespace std;
int main() {
    array<string, 3> a = {"Geeks", "For",
                            "Geeks"};

    // Finding the size
    cout << a.size();
    return 0;
}

3

Time Complexity: O(1)
Auxiliary Space: O(1)

Example 2: Using array::size() on an Uninitialized Array

// C++ Program to find the size of uninitialized
// array using array::size() method
#include <bits/stdc++.h>
using namespace std;
int main() {
    array<int, 3> a;

    // Finding the size
    cout << a.size();
    return 0;
}

3

Time Complexity: O(1)
Auxiliary Space: O(1)

Example 3: Using array::size() on an Array with Initial Size 0.

// C++ Program to implement array::size() method
#include <bits/stdc++.h>
using namespace std;
int main() {
    array<int, 0> a;

    // find the size of an array using array::size() 
    cout << a.size();
    return 0;
}

0

Time Complexity: O(1)
Auxiliary Space: O(1)