leetcode 274. H-Index

class Solution(object):    def hIndex(self, citations):        """        :type citations: List[int]        :rtype: int        """        m = len(citations)        buckets = [0 for i in range(m+1)]        for citation in citations:            if citation >= m:                buckets[m] += 1            else:                buckets[citation] += 1        sum = 0        for i in range(m,-1,-1):            sum += buckets[i]            if sum >= i:                return i        return 0