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 the researcher's h-index.

According to the definition of h-index on Wikipedia: The h-index is defined as the maximum value of h such that the given researcher has published at least h papers that have each been cited at least h times.

Example 1:

Input: citations = [3,0,6,1,5]
Output: 3
Explanation: [3,0,6,1,5] 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, their h-index is 3.

Example 2:

Input: citations = [1,3,1]
Output: 1

Constraints:

• n == citations.length
• 1 <= n <= 5000
• 0 <= citations[i] <= 1000

Code

C++

class Solution
{
public:
    int hIndex(vector<int> &citations)
    {
        sort(citations.begin(), citations.end());
        int maximum = 0;
        int size = citations.size();
        for (int i = 0; i < size; i++)
        {
            if (citations[i] >= size - i)
            {
                maximum = max(maximum, size - i);
            }
        }
        return maximum;
    }
};