Rotation of Elements of Array - Left and Right in Python

Understanding Array Rotation

Array rotation involves shifting elements either to the left or right by a specified number of positions.

We will explore three different methods to perform left and right rotation in Python.

Method 1: Using Slicing

def left_rotate(arr, d):
    return arr[d:] + arr[:d]

def right_rotate(arr, d):
    return arr[-d:] + arr[:-d]

def print_array(arr):
    print(" ".join(map(str, arr)))

arr = [1, 2, 3, 4, 5]
arr = left_rotate(arr, 2)
print("Array after left rotation:")
print_array(arr)
arr = right_rotate(arr, 2)
print("Array after right rotation:")
print_array(arr)
            

Output:

Array after left rotation:
3 4 5 1 2
Array after right rotation:
1 2 3 4 5
            

Method 2: Using Reverse Algorithm

def reverse(arr, start, end):
    while start < end:
        arr[start], arr[end] = arr[end], arr[start]
        start += 1
        end -= 1

def left_rotate(arr, d):
    n = len(arr)
    reverse(arr, 0, d - 1)
    reverse(arr, d, n - 1)
    reverse(arr, 0, n - 1)

def right_rotate(arr, d):
    n = len(arr)
    reverse(arr, 0, n - 1)
    reverse(arr, 0, d - 1)
    reverse(arr, d, n - 1)

def print_array(arr):
    print(" ".join(map(str, arr)))

arr = [1, 2, 3, 4, 5]
left_rotate(arr, 2)
print("Array after left rotation:")
print_array(arr)
right_rotate(arr, 2)
print("Array after right rotation:")
print_array(arr)
            

Output:

Array after left rotation:
3 4 5 1 2
Array after right rotation:
1 2 3 4 5
            

Method 3: Rotating One by One

def left_rotate_one(arr):
    arr.append(arr.pop(0))

def right_rotate_one(arr):
    arr.insert(0, arr.pop())

def left_rotate(arr, d):
    for _ in range(d):
        left_rotate_one(arr)

def right_rotate(arr, d):
    for _ in range(d):
        right_rotate_one(arr)

def print_array(arr):
    print(" ".join(map(str, arr)))

arr = [1, 2, 3, 4, 5]
left_rotate(arr, 2)
print("Array after left rotation:")
print_array(arr)
right_rotate(arr, 2)
print("Array after right rotation:")
print_array(arr)
            

Output:

Array after left rotation:
3 4 5 1 2
Array after right rotation:
1 2 3 4 5