Python program for array rotation

Program to rotate the array R times

# Python program to left rotate array

# Function to rotate arrays in Python
def rotateArrayLeft(arr, R, n):
    for i in range(R):
    	firstVal = arr[0]
    	for i in range(n-1):
    		arr[i] = arr[i+1]
    	arr[n-1] = firstVal

# Taking array input from user
arr = [1, 2, 3, 4, 5, 6, 7]
n = int(input("Enter number of elements of the array: "))
arr = []
print("Enter elements of the array :")
for i in range(n):
  numbers = int(input())
  arr.append(numbers)
R = int(input("Enter rotation count: "))

# Printing array 
print("Initial Array :", end = " ")
for i in range(n):
	print ("%d"% arr[i],end=" ")
	
# Calling function for left Rotating array 
rotateArrayLeft(arr, R, n)

# Printing new array 
print("\nArray after rotation: ", end = " ")
for i in range(n):
	print ("%d"% arr[i],end=" ")

Output:

Enter number of elements of the array: 10
Enter elements of the array :
12
23
34
45
56
67
78
90
10
67
Enter rotation count: 3
Initial Array : 12 23 34 45 56 67 78 90 10 67
Array after rotation:  45 56 67 78 90 10 67 12 23 34

Method 2: Using an extra array to store elements

In this method, we will use an extra array of size R, to store the elements for rotation. We will store the elements in an extra array and then shift every element's R places left. Then put the elements of the array after the last element of after shift.

Algorithm:

1. Store first R elements of the array arr[] to an array shift[].
2. Loop through the array i -> 0 to n-R.
   • arr[i] = arr[i + R].
3. Append elements of shift[] at the end of arr[].
4. Print the array formed after rotation.

Program to rotate array using an extra array

# Python program to left rotate array

# Function to rotate arrays in Python
def rotateArrayLeft(arr, R, n):
    shift = []
    i = 0
    while (i < R):
        shift.append(arr[i])
        i = i + 1
    for i in range(n-R):
    		arr[i] = arr[i+R]
    i = n-R
    j = 0
    while (i < n):
        arr[i] = shift[j]
        j += 1
        i = i + 1
    
    return arr

# Taking array input from user
arr = [1, 2, 3, 4, 5, 6, 7]
n = int(input("Enter number of elements of the array: "))
arr = []
print("Enter elements of the array: ")
for i in range(n):
  numbers = int(input())
  arr.append(numbers)
R = int(input("Enter rotation count: "))

# Printing array 
print("Initial Array: ", end = " ")
for i in range(n):
	print ("%d"% arr[i],end=" ")
	
# Calling function for left Rotating array 
rotateArrayLeft(arr, R, n)

# Printing new array 
print("\nArray after rotation: ", end = " ")
for i in range(n):
	print ("%d"% arr[i],end=" ")

Output:

Enter number of elements of the array: 10
Enter elements of the array:
10
20
30
40
50
60
70
80
90
100
Enter rotation count: 3
Initial Array:  10 20 30 40 50 60 70 80 90 100
Array after rotation:  40 50 60 70 80 90 100 10 20 30

Method 3: Using inbuilt slicing on list

The list slice can directly perform the task as we can slice the array from any index into half and use the sliced part as an array.

Program to rotate array using list slicing

# Python program to left rotate array

# Function to rotate arrays in Python
def rotateArrayLeft(arr, R, n):
    arr[:]=arr[R:n]+arr[0:R]
    return arr

# Taking array input from user
arr = [1, 2, 3, 4, 5, 6, 7]
n = int(input("Enter number of elements of the array: "))
arr = []
print("Enter elements of the array: ")
for i in range(n):
  numbers = int(input())
  arr.append(numbers)
R = int(input("Enter rotation count: "))

# Printing array 
print("Initial Array: ", end = " ")
for i in range(n):
	print ("%d"% arr[i],end=" ")
	
# Calling function for left Rotating array 
rotateArrayLeft(arr, R, n)

# Printing new array 
print("\nArray after rotation: ", end = " ")
for i in range(n):
	print ("%d"% arr[i],end=" ")

Output:

Enter number of elements of the array: 10
Enter elements of the array:
10
20
30
40
50
60
70
80
90
100
Enter rotation count: 3
Initial Array:  10 20 30 40 50 60 70 80 90 100
Array after rotation:  40 50 60 70 80 90 100 10 20 30