532. K-diff Pairs in an Array

• corner case, length less than 2 and negative k.

  	class Solution {
  	// O(n) O(n)
  	public int findPairs(int[] nums, int k) {
  	if (nums.length < 2 || k < 0) return 0;
  	HashSet visited = new HashSet();
  	HashSet pairs = new HashSet();
  	for (int n : nums) {
  	if (visited.contains(n+k)) {
  	pairs.add(n+k < n ? n+k : n);
  	}
  	if (visited.contains(n-k)) {
  	pairs.add(n-k < n ? n-k : n);
  	}
  	visited.add(n);
  	}
  	return pairs.size();
  	}
  	}

  view raw 532_0904.java hosted with ❤ by GitHub
• variant of two sum: O(1) space