275. H-Index II H 指数 II

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/

题目地址: https://leetcode.com/problems/h-index-ii/description/


Given an array of citations sorted in ascending order (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."


Input: citations = [0,1,3,5,6]
Output: 3 
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had 
             received 0, 1, 3, 5, 6 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.


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

Follow up:

This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order. Could you solve it in logarithmic time complexity?


计算某个研究人员的影响因子。影响因子的计算方式是有h篇影响力至少为h的论文。影响因子是衡量作者生产力和影响力的方式,判断了他又多少篇影响力很大的论文。和274. H-Indexopen in new window不同的是,这个题已经排好了序。



274. H-Indexopen in new window中,是先排序再遍历做的,这个题已经排好了序,所以比274更简单,使用二分查找可以快速求解。



class Solution(object):
    def hIndex(self, citations):
        :type citations: List[int]
        :rtype: int
        N = len(citations)
        l, r = 0, N - 1
        H = 0
        while l <= r:
            mid = l + (r - l) / 2
            H = max(H, min(citations[mid], N - mid))
            if citations[mid] < N - mid:
                l = mid + 1
                r = mid - 1
        return H



2018 年 10 月 6 日 —— 努力看书