2006. Count Number of Pairs With Absolute Difference K

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`

2006. Count Number of Pairs With Absolute Difference K
``````struct Solution;

impl Solution {
fn count_k_difference(nums: Vec<i32>, k: i32) -> i32 {
let n = nums.len();
let mut res = 0;
for i in 0..n {
for j in i + 1..n {
if (nums[j] - nums[i]).abs() == k {
res += 1;
}
}
}
res
}
}

#[test]
fn test() {
let nums = vec![1, 2, 2, 1];
let k = 1;
let res = 4;
assert_eq!(Solution::count_k_difference(nums, k), res);
let nums = vec![1, 3];
let k = 3;
let res = 0;
assert_eq!(Solution::count_k_difference(nums, k), res);
let nums = vec![3, 2, 1, 5, 4];
let k = 2;
let res = 3;
assert_eq!(Solution::count_k_difference(nums, k), res);
}
``````
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