Python Program to Split the Array and Add First Part to the End

Given an array and an integer k, the task is to split the array from the kth position and move the first part to the end. For Example:

Input: arr = [12, 10, 5, 6, 52, 36], k = 2
Output: [5, 6, 52, 36, 12, 10]
Explanation: Split the array at index k and move the first part [12, 10] (for k = 2) to the end.

Below are the different methods to perform this task:

Using deque.rotate() from collections

deque from the collections module allows efficient rotation of elements. Its rotate() method handles both left and right rotations internally without explicit shifting.

[5, 6, 52, 36, 12, 10]

Explanation:

• deque(arr): converts the list into a double-ended queue
• rotate(-k): shifts the elements left by k positions
• list(d): converts the deque back into a list

Using List Slicing

List slicing rotates a list by splitting it at position k taking elements from index k to the end first, then adding the first k elements to the end.

[5, 6, 52, 36, 12, 10]

Explanation:

• arr[:k]: first k elements.
• arr[k:]: remaining elements.
• Concatenating them gives the rotated array.

Using List Comprehension and Modulo

This method uses modular arithmetic to calculate rotated positions directly. It constructs a new list where each element is taken from (i + k) % len(arr).

[5, 6, 52, 36, 12, 10]

Explanation:

• (i + k) % len(arr): wraps indices around the array, ensuring the rotation is circular.
• Creates a rotated version without modifying the original array.

Using extend()

Slicing combined with extend() achieves rotation while demonstrating list merging explicitly.

[5, 6, 52, 36, 12, 10]

Explanation:

• arr[:k]: extracts the first k elements.
• arr[k:]: remaining part.
• extend(x): appends the first part to the end.

Related Articles:

• Program for Array Rotation
• Ways to rotate a list