# 275. H-Index II H 指数 II

## # 题目描述：

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."

Example:

``````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.
``````

Note:

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

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?

## # 解题方法

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
else:
r = mid - 1
return H
``````

## # 日期

2018 年 10 月 6 日 —— 努力看书