array::rbegin() and array::rend() in C++ STL

1. array::rbegin() is a built-in function in C++ STL which returns a reverse iterator pointing to the last element in the container. Syntax:

array_name.rbegin()

1. Parameters: The function does not accept any parameter. Return value: The function returns a reverse iterator pointing to the last element in the container. Program to demonstrate the array::rbegin() method: Program 1: 

CPP

// CPP program to illustrate
// the array::rbegin() function
#include <bits/stdc++.h>
using namespace std;

int main()
{
    // array initialisation
    array<int, 5> arr = { 1, 5, 2, 4, 7 };

    // prints the last element
    cout << "The last element is " << *(arr.rbegin()) << endl;

    // prints all the elements
    cout << "The array elements in reverse order are:\n";
    for (auto it = arr.rbegin(); it != arr.rend(); it++)
        cout << *it << " ";

    return 0;
}

Output:

The last element is 7
The array elements in reverse order are:
7 4 2 5 1

Time Complexity: O(N) where N is the size of the array.
Auxiliary Space: O(1)

1. array::rend() is a built-in function in C++ STL which returns a reverse iterator pointing to the theoretical element right before the first element in the array container. Syntax:

array_name.rend()

1. Parameters: The function does not take any parameter. Return value: The function returns a reverse iterator pointing to the theoretical element right before the first element in the array container. Program to demonstrate the array::rend() method: Program 1: 

CPP

// CPP program to illustrate
// the array::rend() function
#include <bits/stdc++.h>
using namespace std;

int main()
{
    array<int, 5> arr = { 1, 5, 2, 4, 7 };

    // prints all the elements
    cout << "The array elements in reverse order are:\n";
    for (auto it = arr.rbegin(); it != arr.rend(); it++)
        cout << *it << " ";
    return 0;
}

Output:

The array elements in reverse order are:
7 4 2 5 1

Time Complexity: O(N) where N is the size of the array.
Auxiliary Space: O(1)