Rotate an Array by K Position using Reversal Algorithm in C#

Back to: Logical Programming with CSharp

Rotate an Array by K Position using Reversal Algorithm in C#

In this article, I am going to discuss Rotate an Array by K Position using Reversal Algorithm in C# with Examples. Please read our previous article where we discussed Rotating an array by K position using Popup and Unshifting Algorithm in C#. Rotation of an array basically means shifting each and every element to specified positions to the left or right.

Rotation of Array using Reversal Algorithm in C#

The Reversal Algorithm is an algorithm to rotate an array by position k with time complexity 0(n) and in place (which means no other array needs to be created).

The Logic of the Reversal Algorithm

Step1:

Suppose the position of rotation is 3 and an input array is:

In this algorithm, the array will be divided into two groups say group 1 and group 2.
Group 1 will be from 0 to (position -1)
Group 2 will be from the position to (n-1)
Where n denotes the length of the array and position denotes the position of the rotation.

Step2:

After dividing the whole array, we need to swap the values of each group with each other.
Group1: arr[0] will be swapped with arr[1]
Group2: arr[2] will be swapped with arr[4]

Step3:

The whole array will be swapped once to get the rotation of the array as output.

Arr[0] will be swapped with Arr[4]
Arr[1] will be swapped with Arr[3]
After performing these 3 simple steps we will get the rotated array as output.

Logic to rotate an array by using Reversal Algorithm

1. Take the value of position from the user.
2. Create a function named swapArray to swap the value with input parameters are array, starIndex, and lastIndex.
3. Call function swapArray with (arr, 0, (position-1))
4. Call function swapArray with (arr,position,(n-1))
5. Call function swapArray with (arr, 0, (n-1))

Example:

The following C# Program performs rotation of array by position k using reversal algorithm.

using System;
namespace DotNetTutorials
{
    public class ReversalAlgorithm
    {
        static void Main(string[] args)
        {
            int[] arr = { 1, 2, 3, 4, 5, 6, 7 };
            Console.WriteLine("Original Array is :");
            for (int i = 0; i < arr.Length; i++)
                Console.Write(arr[i] + " ");

            Console.WriteLine();

            Console.Write("Enter value of k:");
            int position = Convert.ToInt32(Console.ReadLine());
            ReversalAlgorithm obj = new ReversalAlgorithm();
            obj.SwapElements(arr, 0, (position - 1));// 1st part
            obj.SwapElements(arr, position, (arr.Length - 1));//2nd 
            obj.SwapElements(arr, 0, (arr.Length - 1));

            Console.WriteLine();

            Console.WriteLine("Rotation of array by position " + position);
            for (int i = 0; i < arr.Length; i++)
                Console.Write(arr[i] + " ");

            Console.ReadKey();
        }

        //3 times
        void SwapElements(int[] arr, int startIndex, int endIndex)
        {
            while (startIndex < endIndex)
            {
                int temp = arr[startIndex];
                arr[startIndex] = arr[endIndex];
                arr[endIndex] = temp;

                startIndex++;
                endIndex--;
            }
        }
    }
}

Output:

In this article, I am going to discuss How to Reverse an Array in C# with Examples. Here, in this article, I try to explain Rotate an array by K position using Reversal Algorithm in C# with Examples and I hope you enjoy this Rotate an array by position k by using Reversal Algorithm in C# article.