LeetCode - H-Index

Question Definition

Given an array of citations (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.”

For example, given citations = [3, 0, 6, 1, 5], which 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, his h-index is 3.

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

Java Solution

public int hIndex(int[] citations) {
    Arrays.sort(citations);
    for (int i = citations.length - 1; i >= 0; i--) {
        if ((citations.length - i - 1) >= citations[i]) return citations.length - i - 1;
    }
    return citations.length;
}