H-Index II

 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?

class Solution {

public:

    int hIndex(vector<int>& citations) {

        int l=0,h=citations.size()-1,mid;

        int n=h+1;

         

        while(l<=h)

        {

            mid=(l+h)/2;

            if(citations[mid]==(n-mid))

            {return n-mid;}

            else if(citations[mid]>(n-mid))

            { h=mid-1;}

            else

            {  l=mid+1;}

            

        }

        return n-l;

    }

};