532. K-diff Pairs in an Array

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`
• `i != j`
• `|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`

532. K-diff Pairs in an Array
``````struct Solution;

use std::cmp::Ordering::*;
use std::collections::HashMap;
use std::collections::HashSet;

impl Solution {
fn find_pairs(nums: Vec<i32>, k: i32) -> i32 {
let mut res = 0;
let mut hs: HashSet<i32> = HashSet::new();
let mut hm: HashMap<i32, i32> = HashMap::new();
match k.cmp(&0) {
Equal => {
for x in nums {
let e = hm.entry(x).or_default();
if let 1 = *e {
res += 1;
}
*e += 1;
}
}
Greater => {
for x in nums {
if hs.contains(&x) {
continue;
} else {
hs.insert(x);
if hs.contains(&(x + k)) {
res += 1;
}
if hs.contains(&(x - k)) {
res += 1;
}
}
}
}
Less => {}
}
res
}
}

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