Python3 Program for 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)
  reverseArray(arr[], 0, n-1) ;
  reverse(arr[], 0, d-1);
  reverse(arr[], d, n-1);

Below is the implementation of above approach: 

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

Output:

8 9 10 1 2 3 4 5 6 7 

Time Complexity: O(N)

Auxiliary Space: O(1)

Please refer complete article on Reversal algorithm for right rotation of an array for more details!