Right Rotation of an Array

 Reversal algorithm for right rotation of an array

Given an array, right rotate it by k elements. 

After K=3 rotation 

Examples: 

Input: arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} k = 3

Output: 8 9 10 1 2 3 4 5 6 7

Input: arr[] = {121, 232, 33, 43 ,5} k = 2

Output: 43 5 121 232 33

Note : In the below solution, k is assumed to be smaller than or equal to n. We can easily modify the solutions to handle larger k values by doing k = k % n

Algorithm: 

  rotate(arr[], d, n)
  reverse(arr[], 0, n-1) ;
  reverse(arr[], 0, d-1);
  reverse(arr[], d, n-1);

// Java program for right rotation of
// an array (Reversal Algorithm)
import java.io.*;

class Test
{
	// Function to reverse arr[]
	// from index start to end
	static void reverseArray(int arr[], int start,	int end)
	{
		while (start < end)
		{
		int temp = arr[start];
		arr[start] = arr[end];
		arr[end] = temp;
		start++;
		end--;
		}
	}

	// Function to right rotate
	// arr[] of size n by d
	static void rightRotate(int arr[], int d, int n)
	{
	reverseArray(arr, 0, n - 1);
	reverseArray(arr, 0, d - 1);
	reverseArray(arr, d, n - 1);
	}

	// Function to print an array
	static void printArray(int arr[], int size)
	{
	for (int i = 0; i < size; i++)
		System.out.print(arr[i] + " ");
	}

	public static void main (String[] args)
	{
		int arr[] = {1, 2, 3, 4, 5,
					6, 7, 8, 9, 10};
	
	int n = arr.length;
	int k = 3;
	
	rightRotate(arr, k, n);
	printArray(arr, n);
		
	}
}