algorithm notes: leetcode#532 k

class :
    def findPairs(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: int
        """
        cnt = dict()
        for num in nums:
            cnt[num] = cnt.get(num, 0) + 1
        return sum([(k>0 and num+k in cnt) or (k==0 and cnt[num]>1) for num in cnt])