C++ std::array::rbegin

The std::array::rbegin function returns a reverse iterator pointing to the last element of the array (considered the first element of the reversed array). This allows you to iterate over the elements of the array in reverse order.

Syntax of std::array::rbegin

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reverse_iterator rbegin() noexcept;
const_reverse_iterator rbegin() const noexcept;

Parameters

The std::array::rbegin function does not take any parameters.

Return Value

Returns a reverse iterator (or a constant reverse iterator for const arrays) to the last element of the array, which is the first element in reverse order. If the array is empty, the returned iterator will be equal to std::array::rend.

Examples for std::array::rbegin

Example 1: Traversing an Array in Reverse Using std::array::rbegin

This example demonstrates iterating through the elements of a std::array in reverse order using rbegin() and rend():

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#include <iostream>
#include <array>

int main() {
    std::array<int, 5> arr = {10, 20, 30, 40, 50};

    std::cout << "Array elements in reverse order: ";
    for (auto rit = arr.rbegin(); rit != arr.rend(); ++rit) {
        std::cout << *rit << " ";
    }
    std::cout << std::endl;

    return 0;
}

Explanation:

  1. Define an array: A std::array of size 5 is defined and initialized with the elements {10, 20, 30, 40, 50}.
  2. Use rbegin() and rend(): The rbegin() function provides a reverse iterator pointing to the last element of the array, and rend() provides a reverse iterator pointing to one before the first element of the array.
  3. Iterate in reverse: A for loop is used to traverse the array in reverse order, accessing each element using the dereference operator *rit.

Output:

Array elements in reverse order: 50 40 30 20 10

Example 2: Using std::array::rbegin with Standard Algorithms

This example demonstrates using std::array::rbegin with the std::copy algorithm to print elements in reverse order:

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#include <iostream>
#include <array>
#include <iterator>
#include <algorithm>

int main() {
    std::array<int, 5> arr = {1, 2, 3, 4, 5};

    std::cout << "Array elements in reverse order: ";
    std::copy(arr.rbegin(), arr.rend(), std::ostream_iterator<int>(std::cout, " "));
    std::cout << std::endl;

    return 0;
}

Explanation:

  1. Original array: The array arr is initialized with elements {1, 2, 3, 4, 5}.
  2. Use std::copy: The std::copy algorithm is used to copy elements from the range specified by rbegin() and rend() to an output stream iterator, which writes them to the console.
  3. Reverse traversal: The rbegin() function provides the starting point for reverse iteration, and rend() provides the endpoint.

Output:

Array elements in reverse order: 5 4 3 2 1

Exception Handling in std::array::rbegin

The std::array::rbegin function does not throw exceptions as it is marked noexcept. This ensures safe usage for reverse traversal operations.