Python3 Program to Print all possible rotations of a given Array

Given an integer array arr[] of size N, the task is to print all possible rotations of the array.
Examples: 

Input: arr[] = {1, 2, 3, 4} 
Output: {1, 2, 3, 4}, {4, 1, 2, 3}, {3, 4, 1, 2}, {2, 3, 4, 1} 
Explanation: 
Initial arr[] = {1, 2, 3, 4} 
After first rotation arr[] = {4, 1, 2, 3} 
After second rotation arr[] = {3, 4, 1, 2} 
After third rotation arr[] = {2, 3, 4, 1} 
After fourth rotation, arr[] returns to its original form.
Input: arr[] = [1] 
Output: [1] 

Approach: 
Follow the steps below to solve the problem:  

1. Generate all possible rotations of the array, by performing a left rotation of the array one by one.
2. Print all possible rotations of the array until the same rotation of array is encountered.

Below is the implementation of the above approach : 

# Python program to print
# all possible rotations
# of the given array

# Function to reverse array 
# between indices s and e
def reverse(arr, s, e):
    while s < e:
        tem = arr[s]
        arr[s] = arr[e]
        arr[e] = tem
        s = s + 1
        e = e - 1
# Function to generate all
# possible rotations of array
def fun(arr, k):
    n = len(arr)-1
    # k = k % n
    v = n - k
    if v>= 0:
        reverse(arr, 0, v)
        reverse(arr, v + 1, n)
        reverse(arr, 0, n)
        return arr
# Driver Code
arr = [1, 2, 3, 4]
for i in range(0, len(arr)):
    count = 0
    p = fun(arr, i)
    print(p, end =" ")

[1, 2, 3, 4] [4, 1, 2, 3] [2, 3, 4, 1] [3, 4, 1, 2]

Time Complexity: O (N²) 
Auxiliary Space: O (1)

Approach 2: Follow the steps below to solve the problem:  

1. Define the Main class.
2. Define the main method which takes args as input.
3. Create the arr array and get its length n.
4. Create the rotatedArr array with length 2*n and fill it with zeroes.
5. Copy the arr array twice into the rotatedArr array.
6. Loop over the n possible rotations.
7. For each rotation, print a "[" character.
8. Loop over the elements of the rotated array.
9. Print each element followed by a space (if it's not the last element in the rotated array).
10. After the loop, print a "]" character followed by a space.
11. Run the main method if the script is being executed as the main module.

Below is the implementation of the above approach : 

class Main:
    def main(args):
        arr = [1, 2, 3, 4]
        n = len(arr)

        rotatedArr = [0] * (2*n)

        # Copy the array twice into the rotatedArr
        for i in range(n):
            rotatedArr[i] = arr[i]
            rotatedArr[i+n] = arr[i]

        # Generate all possible rotations
        for i in range(n):
            print("[", end="")
            for j in range(i, i+n):
                print(rotatedArr[j], end="")
                if j != i+n-1:
                    print(" ", end="")
            print("] ", end="")


# Nikunj Sonigara
if __name__ == "__main__":
    Main.main(None)

[1 2 3 4] [2 3 4 1] [3 4 1 2] [4 1 2 3] 

Time Complexity: O(N²) 
Auxiliary Space: O(N)

kartik

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Article Tags :

• Python
• Python Programs
• School Programming
• DSA
• Arrays
• rotation

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Practice Tags :

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