LeetCode-in-Java
274. H-Index
Medium
Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper, 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.
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.length1 <= n <= 50000 <= citations[i] <= 1000
Solution
public class Solution {
public int hIndex(int[] citations) {
int len = citations.length;
int[] freqArray = new int[len + 1];
for (int citation : citations) {
freqArray[Math.min(citation, len)]++;
}
int totalSoFar = 0;
for (int k = len; k >= 0; k--) {
totalSoFar += freqArray[k];
if (totalSoFar >= k) {
return k;
}
}
return -1;
}
}