# 275. H-Index II
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.
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?
# Solution
Approach 1: Binary search.
# Code (Python)
Approach 1:
# Code (C++)
Approach 1:
class Solution {
public:
int hIndex(vector<int>& citations) {
int n = citations.size();
int lo = 0;
int hi = n - 1;
while (lo <= hi)
{
int mid = lo + (hi - lo) / 2;
if (citations[mid] < n - mid)
lo = mid + 1;
else if (citations[mid] > n - mid)
hi = mid - 1;
else
return n - mid;
}
return n - lo;
}
};