原题是：

Screen Shot 2017-11-22 at 12.14.12 PM.png

思路是：

两指针。
要注意的是K为0，和为负数的corner case。
Python里list去重的方法，我经常使用：list(set(nums))

代码是：

class Solution:
    def findPairs(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: int
        """
        if k < 0 :
            return 0
        elif k != 0:
            noDup = list(set(nums))
            noDup = sorted(noDup)
            cnt, i ,j = 0, 0, 1
            while i < len(noDup) and j < len(noDup):
                if noDup[j] - noDup[i] == k:
                    cnt += 1
                    i += 1
                    j += 1
                elif noDup[j] - noDup[i] > k:
                    i += 1
                else:
                    j += 1
        else:
            nums = sorted(nums)
            candidate = []
            cnt = 0
            for i in range(len(nums)):
                if i < len(nums)-1 and nums[i] == nums[i+1]:
                    candidate.append(nums[i])
            cnt = len(list(set(candidate)))
        
        return cnt