LeetCode [532] K-diff Pairs in an Array

 532. K-diff Pairs in an Array

Medium

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

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class Solution { public int findPairs(int[] nums, int k) { Arrays.sort(nums); int n = nums.length; int cnt = 0; Set<Integer> set = new HashSet<>(); for(int i=0; i<n; ++i){ if(i>0 && nums[i]==nums[i-1]){ if(k>0) continue; if(k==0 && i>1 && nums[i-1]==nums[i-2]) continue; } int v = nums[i]; if(set.contains(v-k)) cnt += 1; set.add(v); } return cnt; } }