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Python Program for Reversal algorithm for array rotation

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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] 
Array

Rotation of the above array by 2 will make an array

ArrayRotation1

Python Program for Reversal Algorithm of Array Rotation

Python3
# 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

Python3
# 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)
 

Output
3
4
5
6
7
1
2

Python Program for Reversal Algorithm Using collections.deque

Python3
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)

Output
Rotated array: [3, 4, 5, 6, 7, 1, 2]

Time complexity: O(n + k).
Auxiliary space: O(n)


Last Updated : 26 Mar, 2024
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