532. K-diff Pairs in an Array

Problem:

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Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array. Here a k-diff pair is defined as an integer pair (i, j), where i and j are both numbers in the array and their absolute difference is k.

Example 1:

Input: [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:[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: [1, 3, 1, 5, 4], k = 0
Output: 1
Explanation: There is one 0-diff pair in the array, (1, 1).

Analysis:
通过这道题可以总结一条规律。同向双指针fast pointer不需要去重。

Solution:

class Solution {
    public int findPairs(int[] nums, int k) {
        if (nums == null || nums.length == 0)
            return 0;
        int len = nums.length, j = 0, res = 0;
        Arrays.sort(nums);
        for (int i = 0; i < len; i++) {
            j = i + 1;
            while (j < len ) {
                if (j < len && nums[j] - nums[i] == k)
                {
                     res++;    
                     break;
                }
                j++;
            }
            while (i < len - 1 && nums[i] == nums[i + 1]) i++;
        }
        return res;
    }
}