class Solution:
    def hIndex(self, citations: List[int]) -> int:
        citations.sort(reverse=True)

        h = 0
        for index, c in enumerate(citations):
            if c >= index + 1:
                h = index + 1
            else:
                break

        return h

class Solution:
    def hIndex(self, citations: List[int]) -> int:
        n = len(citations)
        counts = [0]*(n+1)

        # buckets the 
        for c in citations:
            if c>=n:
                counts[n] += 1
            else:
                counts[c] += 1

        total = 0
        for i in range(n, -1, -1):
            total += counts[i]
            if total >= i:
                return i

        return 0