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# 0532. K-diff Pairs in an Array

<https://leetcode.com/problems/k-diff-pairs-in-an-array>

## Description

Given an array of integers `nums` and an integer `k`, return *the number of **unique** k-diff pairs in the array*.

A **k-diff** pair is an integer pair `(nums[i], nums[j])`, where the following are true:

* `0 <= i < j < nums.length`
* `|nums[i] - nums[j]| == k`

**Notice** that `|val|` denotes the absolute value of `val`.

**Example 1:**

```
**Input:** nums = [3,1,4,1,5], k = 2
**Output:** 2
**Explanation:** There are two 2-diff pairs in the array, (1, 3) and (3, 5).
Although we have two 1s in the input, we should only return the number of **unique** pairs.
```

**Example 2:**

```
**Input:** nums = [1,2,3,4,5], k = 1
**Output:** 4
**Explanation:** There are four 1-diff pairs in the array, (1, 2), (2, 3), (3, 4) and (4, 5).
```

**Example 3:**

```
**Input:** nums = [1,3,1,5,4], k = 0
**Output:** 1
**Explanation:** There is one 0-diff pair in the array, (1, 1).
```

**Example 4:**

```
**Input:** nums = [1,2,4,4,3,3,0,9,2,3], k = 3
**Output:** 2
```

**Example 5:**

```
**Input:** nums = [-1,-2,-3], k = 1
**Output:** 2
```

**Constraints:**

* `1 <= nums.length <= 104`
* `-107 <= nums[i] <= 107`
* `0 <= k <= 107`

## ac

```java
```