Solution: K-diff Pairs in an Array

Statement

Given an integer array nums and an integer k, return the number of unique pairs of values (a, b) such that a and b both appear in nums and |a - b| = k.

A pair is considered unique based on its values, not on the indices where those values occur in nums.

Note: When k = 0, a valid pair requires a value to appear at least twice in nums.

Constraints:

• $1 \leq$ nums.length $\leq 10^4$

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