K diff pairs in an array

Array Hash Table Two Pointers Binary Search Sorting

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Feb 19, 2026

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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.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

use std::collections::HashMap;
impl Solution {
  pub fn find_pairs(nums: Vec<i32>, k: i32) -> i32 {
    if k < 0 { return 0; }
    let mut map: HashMap<i32, i32> = HashMap::new();
    for &n in &nums { *map.entry(n).or_insert(0) += 1; }
    let mut count = 0i32;
    for (&key, &val) in &map {
      if k == 0 {
        if val >= 2 { count += 1; }
      } else {
        if map.contains_key(&(key + k)) { count += 1; }
      }
    }
    count
  }
}