2006. Count Number of Pairs With Absolute Difference K

https://leetcode.com/problems/count-number-of-pairs-with-absolute-difference-k

Description

Given an integer array nums and an integer k, return the number of pairs (i, j) where i < j such that |nums[i] - nums[j]| == k.

The value of |x| is defined as:

• x if x >= 0.

• -x if x < 0.

Example 1:

**Input:** nums = [1,2,2,1], k = 1
**Output:** 4
**Explanation:** The pairs with an absolute difference of 1 are:
- [**1**,**2**,2,1]
- [**1**,2,**2**,1]
- [1,**2**,2,**1**]
- [1,2,**2**,**1**]

Example 2:

**Input:** nums = [1,3], k = 3
**Output:** 0
**Explanation:** There are no pairs with an absolute difference of 3.

Example 3:

**Input:** nums = [3,2,1,5,4], k = 2
**Output:** 3
**Explanation:** The pairs with an absolute difference of 2 are:
- [**3**,2,**1**,5,4]
- [**3**,2,1,**5**,4]
- [3,**2**,1,5,**4**]

Constraints:

• 1 <= nums.length <= 200

• 1 <= nums[i] <= 100

• 1 <= k <= 99

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