274. H-Index[M]

https://leetcode.com/problems/h-index/

Description

Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher’s h-index.

According to the definition of h-index on Wikipedia: “A scientist has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each.”

Example:

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Input: citations = [3,0,6,1,5]
Output: 3 
Explanation: [3,0,6,1,5] means the researcher has 5 papers in total and each of them had 
             received 3, 0, 6, 1, 5 citations respectively. 
             Since the researcher has 3 papers with at least 3 citations each and the remaining 
             two with no more than 3 citations each, her h-index is 3.

Note: If there are several possible values for h, the maximum one is taken as the h-index.

Solution

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class Solution:
    def hIndex(self, citations: List[int]) -> int:
        ls = len(citations)
        papers = [0] * (ls + 1)
        for c in citations:
            papers[min(ls, c)] += 1
        k, s = ls, papers[ls]
        while k > s:
            k -= 1
            s += papers[k]
        return k