K-diff Pairs in an Array

用哈希表就行了

class Solution(object):
    def findPairs(self, nums, k):
        """
        :type nums: List[int]
        :type k: int
        :rtype: int
        """
        if k < 0:
            return 0

        store = collections.Counter(nums)
        result = 0

        for key, value in store.iteritems():
            if k != 0 and key + k in store:
                result += 1
            if not k:
                result = result + 1 if value >= 2 else result

        return result