# H-Index II -- LeetCode

Datetime:2016-08-23 01:20:41         Topic: LeetCode          Share        Original >>

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."

For example, given  `citations = [3, 0, 6, 1, 5]` , which 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, his h-index is  `3` .

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

Follow up for  H-Index : What if the  `citations` array is sorted in ascending order? Could you optimize your algorithm?

``` 1 class Solution {
2 public:
3     int hIndex(vector<int>& citations) {
4         int left = 0, right = citations.size() - 1;
5         while (left <= right) {
6             int mid = left + (right - left) / 2;
7             if (citations[mid] < citations.size() - mid)
8                 left = mid + 1;
9             else if (mid > left && citations[mid - 1] >= citations.size() - (mid - 1))
10                 right = mid - 1;
11             else return citations.size() - mid;
12         }
13         return 0;
14     }
15 };
```