Given an array of integers, nums, and an integer k, the task is to find the total number of subarrays whose sum is divisible by k. A subarray is a contiguous portion of the array.
Input: nums = [3, 1, 4, 1], k = 3
Output: 3
Explanation: The subarrays whose sum is divisible by 3 are: [3], [1, 4, 1], [3, 1, 4, 1].
Input: nums = [5, 10, -5, 20], k = 7
Output: 0
Explanation: There is no subarray whose sum is divisible by 7.
Input: nums = [4, 5, 0, -2, -3, 1], k = 5