Array Rotation Techniques in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output after rotating array left by 2 positions

What is the output of the following Python code that rotates an array to the left by 2 positions?

DSA Python

arr = [10, 20, 30, 40, 50]
rotations = 2
rotated = arr[rotations:] + arr[:rotations]
print(rotated)

A [30, 40, 50, 10, 20]

B [40, 50, 10, 20, 30]

C [50, 10, 20, 30, 40]

D [20, 30, 40, 50, 10]

💡 Hint

Think about how slicing works for left rotation.

The code slices the array from index 2 to the end, then adds the first two elements at the end. This results in the array rotated left by 2 positions.

❓ Predict Output

intermediate

Output after rotating array right by 3 positions

What is the output of this Python code that rotates an array to the right by 3 positions?

DSA Python

arr = [1, 2, 3, 4, 5, 6]
rotations = 3
rotated = arr[-rotations:] + arr[:-rotations]
print(rotated)

A [5, 6, 1, 2, 3, 4]

B [4, 5, 6, 1, 2, 3]

C [3, 4, 5, 6, 1, 2]

D [6, 1, 2, 3, 4, 5]

💡 Hint

Right rotation means taking last elements to front.

The code takes the last 3 elements and places them at the front, then adds the rest after.

🔧 Debug

advanced

Identify the error in this array rotation code

What error does this code raise when trying to rotate an array left by n positions?

DSA Python

def rotate_left(arr, n):
    n = n % len(arr)
    return arr[n:] + arr[n]

print(rotate_left([1, 2, 3, 4], 2))

A SyntaxError: invalid syntax

B IndexError: list index out of range

C TypeError: can only concatenate list (not "int") to list

D No error, output: [3, 4, 1, 2]

💡 Hint

Look at what arr[n] returns and what is being concatenated.

arr[n] returns a single element (an int), but arr[n:] is a list. Adding a list and an int causes a TypeError.

❓ Predict Output

advanced

Output after rotating array right by length of array

What is the output of this code that rotates an array right by its own length?

DSA Python

arr = [7, 8, 9]
rotations = len(arr)
rotated = arr[-rotations:] + arr[:-rotations]
print(rotated)

A [7, 8, 9]

B []

C [8, 9, 7]

D [9, 7, 8]

💡 Hint

Rotating by array length should return the original array.

Rotating an array by its length results in the same array because the elements cycle back to original positions.

🧠 Conceptual

expert

Minimum rotations to restore original array

Given an array of length 6, what is the minimum number of right rotations needed to restore the array to its original order?

A 0

B 1

C 3

D 6

💡 Hint

Think about how many rotations bring the array back to start.

Rotating right by the array length (6) returns the array to its original order. Smaller rotations do not restore it fully.