Leetcode 275. H-Index II

Problem

Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper and citations is sorted in ascending order, return the researcher's h-index.

According to the definition of h-index on Wikipedia: The h-index is defined as the maximum value of h such that the given researcher has published at least h papers that have each been cited at least h times.

You must write an algorithm that runs in logarithmic time.

Algorithm

Bineary search.

Code

class Solution:
    def hIndex(self, citations: List[int]) -> int:
        K = len(citations)
        if 1 == K:
            return (citations[0] >= 1) * 1
        
        L, R, = 0, len(citations) - 1
        while L < R:
            Mid = (L + R) // 2
            if citations[Mid] >= K - Mid:
                R = Mid
            else: L = Mid + 1

        while L <= R and citations[L] < K - L:
            L += 1
        return K - L