2964. Number of Divisible Triplet Sums

Given a 0-indexed integer array nums and an integer d, return the number of triplets (i, j, k) such that i < j < k and (nums[i] + nums[j] + nums[k]) % d == 0.

Example 1:

Input: nums = [3,3,4,7,8], d = 5
Output: 3
Explanation: The triplets which are divisible by 5 are: (0, 1, 2), (0, 2, 4), (1, 2, 4).
It can be shown that no other triplet is divisible by 5. Hence, the answer is 3.

Example 2:

Input: nums = [3,3,3,3], d = 3
Output: 4
Explanation: Any triplet chosen here has a sum of 9, which is divisible by 3. Hence, the answer is the total number of triplets which is 4.

Example 3:

Input: nums = [3,3,3,3], d = 6
Output: 0
Explanation: Any triplet chosen here has a sum of 9, which is not divisible by 6. Hence, the answer is 0.

Constraints:

• 1 <= nums.length <= 1000
• 1 <= nums[i] <= 109
• 1 <= d <= 109