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Python Program to Rotate an Array

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Array Rotation

Python program for array rotation has been shown here. An array rotation is described as the rotation of array elements to either left or right by k positions.


Example 1: Left rotation

Given array A[] = {10, 20, 30, 40, 50, 60}, k = 2

Rotate elements of A[] by 1 position to the left.

=>A[] = {20, 30, 40, 50, 60, 10}

Again rotate elements of A[] by 1 position to the left.

=>A[] = {30, 40, 50, 60, 10, 20}

So, array A[] after left rotation by 2 positions: {30, 40, 50, 60, 10, 20}



Example 2: Right rotation

Given array A[] = {10, 20, 30, 40, 50, 60}, k = 2

Rotate elements of A[] by 1 position to the right.

=>A[] = {60, 10, 20, 30, 40, 50}

Again rotate elements of A[] by 1 position to the left.

=>A[] = {50, 60, 10, 20, 30, 40}

So, array A[] after right rotation by 2 positions: {50, 60, 10, 20, 30, 40}






1. Python program & output to Rotate an Array

Code has been copied
# ***********************************
#         alphabetacoder.com
# Python program to rotate an array
# ***********************************

# function to left shift the array
def leftShift(arr, s):
    # take input of the number of position of rotation
    k = int(input("Enter the number of position to be left shifted: "))
    # left shift the array upto k position
    for i in range(0, k):
        # get the first elements
        e = arr[0]
        # shift the elements
        for j in range(0, s - 1):
            arr[j] = arr[j + 1]

        arr[s - 1] = e

    # display the finalarray
    print("Output array: ", arr)


# function to right shift the array
def rightShift(arr, s):
    # take input of the number of position of rotation
    k = int(input("Enter the number of position to be right shifted: "))
    # right shift the array upto k position
    for i in range(0, k):
        # get the last elements
        e = arr[s - 1]
        # shift the elements
        for j in range(s - 1, -1, -1):
            arr[j] = arr[j - 1]

        arr[0] = e
    # display the final array
    print("Output array: ", arr)


def main():
    # take input
    s = int(input("Enter the size of array: "))

    # declare an array of size s
    arr = [0] * s

    # take input
    print("Enter the elements of array: ")
    for i in range(0, s):
        arr[i] = int(input(""))

    # take input of the direction of rotation
    print("Enter the direction of rotation: ")
    print("1. Left rotation")
    print("2. Right rotation")
    d = int(input("Your choice >> "))

    # call function as per choice
    if d == 1:
        leftShift(arr, s)
    elif d == 2:
        rightShift(arr, s)
    else:
        print("Wrong Choice!")


# driver code
main()

Output

Enter the size of array: 5

Enter the elements of array:

0

5

10

15

20

Enter the direction of rotation:

1. Left rotation

2. Right rotation

Your choice >> 1

Enter the number of position to be left shifted: 3

Output array: [15, 20, 0, 5, 10]




2. Time complexity to Rotate an Array


Time Complexity: O(n * k)

Here, $n$ elements in an array are to be rotated by $k$ positions to either left or right.





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