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

Rust Solution

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);
}

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