Subarray Sums Divisible by K

You are given an integer array nums and an integer k, return the number of non-empty subarrays that have a sum divisible by k.

A subarray is a contiguous part of an array.

Example 1:

Input: nums = [4,5,0,-2,-3,1], k = 5

Output: 7

Explanation: There are 7 subarrays with a sum divisible by k = 5:
[4, 5, 0, -2, -3, 1], [5], [5, 0], [5, 0, -2, -3], [0], [0, -2, -3], [-2, -3]

Example 2:

Input: nums = [5], k = 9

Output: 0

Constraints:

• 1 <= nums.length <= 30,000
• -10,000 <= nums[i] <= 10,000
• 2 <= k <= 10,000