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);

Below is the implementation of above approach: 

C++

// C++ program for right rotation of
// an array (Reversal Algorithm)
#include <bits/stdc++.h>

/*Function to reverse arr[]
from index start to end*/
void reverseArray(int arr[], int start,
                            int end)
{
    while (start < end)
    {
        std::swap(arr[start], arr[end]);
        start++;
        end--;
    }
}

/* Function to right rotate arr[]
of size n by d */
void rightRotate(int arr[], int d, int n)
{
    // if in case d>n,this will give segmentation fault.
    d=d%n;
    reverseArray(arr, 0, n-1);
    reverseArray(arr, 0, d-1);
    reverseArray(arr, d, n-1);
}

/* function to print an array */
void printArray(int arr[], int size)
{
    for (int i = 0; i < size; i++)
        std::cout << arr[i] << " ";
}

// driver code
int main()
{
    int arr[] = {1, 2, 3, 4, 5,
                6, 7, 8, 9, 10};

    int n = sizeof(arr)/sizeof(arr[0]);
    int k = 3;

    rightRotate(arr, k, n);
    printArray(arr, n);

    return 0;
}

Java

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

class GFG
{
    // 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);

    }
}
// This code is contributed by Gitanjali.

Python3

# Python3 program for right rotation of
# an array (Reversal Algorithm)


# Function to reverse arr
# from index start to end
def reverseArray( arr, start, end):

    while (start < end):

        arr[start], arr[end] = arr[end], arr[start]
        start = start + 1
        end = end - 1


# Function to right rotate arr
# of size n by d
def rightRotate( arr, d, n):

    reverseArray(arr, 0, n - 1);
    reverseArray(arr, 0, d - 1);
    reverseArray(arr, d, n - 1);


# function to print an array
def printArray( arr, size):
    for i in range(0, size):
        print (arr[i], end = ' ')


# Driver code
arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
n = len(arr)
k = 3

# Function call
rightRotate(arr, k, n)
printArray(arr, n)


# This article is contributed
# by saloni1297

C#

// C# program for right rotation of
// an array (Reversal Algorithm)
using System;

class GFG {

    // 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++)
            Console.Write(arr[i] + " ");
    }

    // Driver code
    public static void Main ()
    {
        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);

    }
}

// This code is contributed by vt_m.

PHP

<?php
// PHP program for right rotation of
// an array (Reversal Algorithm)

/*Function to reverse arr[]
from index start to end*/
function reverseArray(&$arr, $start, $end)
{
    while ($start < $end)
    {
        $temp = $arr[$start];
        $arr[$start] = $arr[$end];
        $arr[$end] = $temp;
        $start++;
        $end--;
    }
}

/* Function to right rotate arr[]
of size n by d */
function rightRotate(&$arr, $d, $n)
{
    reverseArray($arr, 0, $n - 1);
    reverseArray($arr, 0, $d - 1);
    reverseArray($arr, $d, $n - 1);
}

/* function to print an array */
function printArray(&$arr, $size)
{
    for ($i = 0; $i < $size; $i++)
        echo $arr[$i] . " ";
}

// Driver code
$arr = array(1, 2, 3, 4, 5,
             6, 7, 8, 9, 10);

$n = sizeof($arr);
$k = 3;

rightRotate($arr, $k, $n);
printArray($arr, $n);

// This code is contributed by ita_c
?>

Javascript

<script>
// JavaScript program for right rotation of
// an array (Reversal Algorithm)

/*Function to reverse arr[]
from index start to end*/
function reverseArray(arr, start, end){
    while (start < end){
        let temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }
    return arr;
}

/* Function to right rotate arr[]
of size n by d */
function rightRotate(arr, d, n){
    arr = reverseArray(arr, 0, n-1);
    arr = reverseArray(arr, 0, d-1);
    arr = reverseArray(arr, d, n-1);
    return arr;
}

/* function to print an array */
function printArray( arr, size){
    for (let i = 0; i < size; i++)
        document.write( arr[i] + " ");
}

// driver code
let arr = [1, 2, 3, 4, 5,
                6, 7, 8, 9, 10];

let n = arr.length;
let k = 3;

arr = rightRotate(arr, k, n);
printArray(arr, n);

</script>

Output

8 9 10 1 2 3 4 5 6 7 

Time Complexity: O(n), as we are using a while loop to traverse N times.
Auxiliary Space: O(1), as we are not using any extra space.

This article is contributed by Aditya Ranjan. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.