Python Program for Array Rotation Using Rotate one by one

Q: What is Python Program for Array Rotation Using Rotate one by one?

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Q: How to use Python Program for Array Rotation Using Rotate one by one in Python?

Write a function rotate(ar[], d, n) that rotates arr[] of size n by d elements.

Python Program for Array Rotation Using temp array

leftRotate(arr[], d, n)
start
  For i = 0 to i < d
    Left rotate all elements of arr[] by one
end

To rotate by one, store arr[0] in a temporary variable temp, move arr[1] to arr[0], arr[2] to arr[1] …and finally temp to arr[n-1]

Let us take the same example arr[] = [1, 2, 3, 4, 5, 6, 7], d = 2

Rotate arr[] by one 2 times We get [2, 3, 4, 5, 6, 7, 1] after first rotation and [ 3, 4, 5, 6, 7, 1, 2] after second rotation.

Python3

#Function to left rotate arr[] of size n by d*/
def leftRotate(arr, d, n):
    for i in range(d):
        leftRotatebyOne(arr, n)
 
#Function to left Rotate arr[] of size n by 1*/ 
def leftRotatebyOne(arr, n):
    temp = arr[0]
    for i in range(n-1):
        arr[i] = arr[i+1]
    arr[n-1] = temp
         
 
# utility function to print an array */
def printArray(arr,size):
    for i in range(size):
        print ("%d"% arr[i],end=" ")
 
  
# Driver program to test above functions */
arr = [1, 2, 3, 4, 5, 6, 7]
leftRotate(arr, 2, 7)
printArray(arr, 7)
 
# This code is contributed by Shreyanshi Arun

Output

3 4 5 6 7 1 2

Time complexity : O(n * d)
Auxiliary Space : O(1)

Python Program for Array Rotation Using 4 Juggling Algorithm

This is an extension of method 2. Instead of moving one by one, divide the array in different sets
where number of sets is equal to GCD of n and d and move the elements within sets.
If GCD is 1 as is for the above example array (n = 7 and d =2), then elements will be moved within one set only, we just start with temp = arr[0] and keep moving arr[I+d] to arr[I] and finally store temp at the right place.
Here is an example for n =12 and d = 3. GCD is 3 and

Let arr[] be {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}

a)    Elements are first moved in first set – (See below diagram for this movement

          arr[] after this step --> {4 2 3 7 5 6 10 8 9 1 11 12}

b)    Then in second set.
          arr[] after this step --> {4 5 3 7 8 6 10 11 9 1 2 12}

c)    Finally in third set.
          arr[] after this step --> {4 5 6 7 8 9 10 11 12 1 2 3}

Python3

# Function to left rotate arr[] of size n by d
def leftRotate(arr, d, n):
    for i in range(gcd(d, n)):
 
        # move i-th values of blocks
        temp = arr[i]
        j = i
        while 1:
            k = j + d
            if k >= n:
                k = k - n
            if k == i:
                break
            arr[j] = arr[k]
            j = k
        arr[j] = temp
 
# UTILITY FUNCTIONS
# function to print an array
 
 
def printArray(arr, size):
    for i in range(size):
        print("%d" % arr[i], end=" ")
 
# Function to get gcd of a and b
 
 
def gcd(a, b):
    if b == 0:
        return a
    else:
        return gcd(b, a % b)
 
 
# Driver program to test above functions
arr = [1, 2, 3, 4, 5, 6, 7]
leftRotate(arr, 2, 7)
printArray(arr, 7)

Output

3 4 5 6 7 1 2

Time complexity : O(n)
Auxiliary Space : O(1)

Another Approach : Using List slicing

Python3

# Python program using the List 
# slicing approach to rotate the array
def rotateList(arr,d,n):
  arr[:]=arr[d:n]+arr[0:d]
  return arr
# Driver function to test above function 
arr = [1, 2, 3, 4, 5, 6] 
print(arr) 
print("Rotated list is") 
print(rotateList(arr,2,len(arr)))  
 
# this code is contributed by virusbuddah

Output

[1, 2, 3, 4, 5, 6]
Rotated list is
[3, 4, 5, 6, 1, 2]

If array needs to be rotated by more than its length then mod should be done.

For example: rotate arr[] of size n by d where d is greater than n. In this case d%n should be calculated and rotate by the result after mod.

Time complexity : O(n) where n is size of given array
Auxiliary Space : O(1)

Please refer complete article on Program for array rotation for more details!