275.HIndex.cs

// 275. H-Index II

// Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper and citations is sorted in an ascending order, 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.

// You must write an algorithm that runs in logarithmic time.

// Example 1:
// 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, their h-index is 3.
// Example 2:
// Input: citations = [1,2,100]
// Output: 2


public class Solution {
    public int HIndex(int[] citations) {
        int left, right, mid;
        left = 1;
        right = citations.Length;
        int result = 0;
        while (left <= right)
        {
            mid = left + (right - left) / 2;
            if (citations[citations.Length - mid]>= mid)
            {
                result = mid;
                left = mid + 1;
            }
            else
            {
                right = mid - 1;
            }
        }
        return result;
    }
}