Count Pairs with Difference K

Given an array of unique integers `nums` and an integer `k`, return the number of pairs `(i, j)` where `i < j` such that `|nums[i] - nums[j]| == k`. ### Constraints - `1 <= nums.length <= 10^5` - `0 <= nums[i] <= 10^9` - `1 <= k <= 10^9` - All elements of `nums` are unique. ### Input Format - Line 1: An integer `k`. - Line 2: Space-separated integers representing `nums`. ### Output Format Print the number of valid pairs.