0532 - K-diff Pairs in an Array

Description (leetcode)

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).

Constraints:

• 1 <= nums.length <= 10⁴
• −10⁷ <= nums[i] <= 10⁷
• 0 <= k <= 10⁷

submission

use std::collections::HashSet;

impl Solution {
    pub fn find_pairs(nums: Vec<i32>, k: i32) -> i32 {
        nums.into_iter()
            .fold(
                (HashSet::new(), HashSet::new()),
                |(mut result, mut seen), val| {
                    if seen.contains(&(val - k)) {
                        result.insert(val - k);
                    }
                    if seen.contains(&(val + k)) {
                        result.insert(val);
                    }
                    seen.insert(val);
                    (result, seen)
                },
            )
            .0
            .len() as i32
    }
}