Find H-Index.cpp

class Solution {
public:
    int hIndex(vector<int>& citations) {
        sort(citations.begin(),citations.end());
        
        int n = citations.size();
        if(n==0)
            return 0;
        if(citations[0]>=n)
            return n;
        int high = n-1;
        int low=0;
        int mid;
        int candidate = 0;
        
        while(low<=high)
        {
            mid=low+(high-low)/2;
            if(citations[mid]>=n-mid)
            {
                candidate = n-mid;
                high = mid-1;
            }
            else
                low = mid + 1;
        }
        return candidate;
    }
};