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 };