274. H-Index

Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper, return compute the researcher’s h-index.

According to the definition of h-index on Wikipedia: A scientist has an index h if h of their n papers have at least h citations each, and the other n − h papers have no more than h citations each.

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

class Solution {
public:
    int hIndex(vector<int>& citations) {
        sort(citations.begin(), citations.end());
        int h = 0, sz = citations.size(), res;
        while(end(citations) - lower_bound(begin(citations), end(citations), h) >= h) {
              res = h++;
        }
        return res;
    }
};