public class Solution
extends Object
2367 - Number of Arithmetic Triplets\.
Easy
You are given a **0-indexed** , **strictly increasing** integer array `nums` and a positive integer `diff`. A triplet `(i, j, k)` is an **arithmetic triplet** if the following conditions are met:
* `i < j < k`,
* `nums[j] - nums[i] == diff`, and
* `nums[k] - nums[j] == diff`.
Return _the number of unique **arithmetic triplets**._
**Example 1:**
**Input:** nums = [0,1,4,6,7,10], diff = 3
**Output:** 2
**Explanation:**
(1, 2, 4) is an arithmetic triplet because both 7 - 4 == 3 and 4 - 1 == 3.
(2, 4, 5) is an arithmetic triplet because both 10 - 7 == 3 and 7 - 4 == 3.
**Example 2:**
**Input:** nums = [4,5,6,7,8,9], diff = 2
**Output:** 2
**Explanation:**
(0, 2, 4) is an arithmetic triplet because both 8 - 6 == 2 and 6 - 4 == 2.
(1, 3, 5) is an arithmetic triplet because both 9 - 7 == 2 and 7 - 5 == 2.
**Constraints:**
* `3 <= nums.length <= 200`
* `0 <= nums[i] <= 200`
* `1 <= diff <= 50`
* `nums` is **strictly** increasing.