Python Program for Reversal algorithm for array rotation
Last Updated :
23 Jul, 2025
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Write a function rotate(arr[], d, n) that rotates arr[] of size n by d elements. In this article, we will explore the Reversal Algorithm for array rotation and implement it in Python.
Example
Input: arr[] = [1, 2, 3, 4, 5, 6, 7] d = 2 Output: arr[] = [3, 4, 5, 6, 7, 1, 2]
Rotation of the above array by 2 will make an array
Python Program for Reversal Algorithm of Array Rotation
# Function to reverse arr[]
def rverseArray(arr,d):
c=(arr[d:])+(arr[:d])
return c
# Driver function to test above functions
arr = [1, 2, 3, 4, 5, 6, 7]
d=2
print(rverseArray(arr,d))
Output
[3, 4, 5, 6, 7, 1, 2]
Python Program for Reversal algorithm for Array Rotation
# Python program for reversal algorithm of array rotation
# Function to reverse arr[] from index start to end
def rverseArray(arr, start, end):
while (start < end):
temp = arr[start]
arr[start] = arr[end]
arr[end] = temp
start += 1
end = end-1
# Function to left rotate arr[] of size n by d
def leftRotate(arr, d):
n = len(arr)
rverseArray(arr, 0, d-1)
rverseArray(arr, d, n-1)
rverseArray(arr, 0, n-1)
# Function to print an array
def printArray(arr):
for i in range(0, len(arr)):
print (arr[i])
# Driver function to test above functions
arr = [1, 2, 3, 4, 5, 6, 7]
leftRotate(arr, 2) # Rotate array by 2
printArray(arr)
# Python program for reversal algorithm of array rotation # Function to reverse arr[] from index start to enddef rverseArray(arr, start, end): while (start < end): temp = arr[start] arr[start] = arr[end] arr[end] = temp start += 1 end = end-1# Function to left rotate arr[] of size n by ddef leftRotate(arr, d): n = len(arr) rverseArray(arr, 0, d-1) rverseArray(arr, d, n-1) rverseArray(arr, 0, n-1) # Function to print an arraydef printArray(arr): for i in range(0, len(arr)): print (arr[i]) # Driver function to test above functionsarr = [1, 2, 3, 4, 5, 6, 7]leftRotate(arr, 2) # Rotate array by 2printArray(arr)Output
3 4 5 6 7 1 2
Python Program for Reversal Algorithm Using collections.deque
from collections import deque
def rotate_array_deque(arr, d):
n = len(arr)
rotated_array = deque(arr)
rotated_array.rotate(-d)
return list(rotated_array)
# Example
arr = [1, 2, 3, 4, 5, 6, 7]
d = 2
rotated_array = rotate_array_deque(arr, d)
print("Rotated array:", rotated_array)
from collections import dequedef rotate_array_deque(arr, d): n = len(arr) rotated_array = deque(arr) rotated_array.rotate(-d) return list(rotated_array)# Examplearr = [1, 2, 3, 4, 5, 6, 7]d = 2rotated_array = rotate_array_deque(arr, d)print("Rotated array:", rotated_array)Output
Rotated array: [3, 4, 5, 6, 7, 1, 2]
Time complexity: O(n + k).
Auxiliary space: O(n)
