Longest Contiguous Subarray

You are given an array of integers and an integer k. Your task is to write a function that finds the length of the longest contiguous subarray in which the difference between the maximum and minimum elements is less than or equal to k.

For example:

• Input:
  • arr = [4, 2, 2, 2, 4, 4, 2, 2]
  • k = 2
• Expected Output: 8

In the above example, the entire array is a valid subarray since the maximum element is 4, the minimum element is 2, and their difference (4 - 2 = 2) does not exceed k.

Your solution should address the following requirements:

1. Implement a function that accepts the array and the integer k as inputs and returns the length of the longest valid contiguous subarray.

2. Assume the input array can contain both positive and negative integers and could be large. Aim for an efficient solution.

3. Write clean and modular code, and consider edge cases such as empty arrays or arrays consisting of a single element.

Feel free to use any programming language you prefer.