274. H-Index

Question

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.”

Example:

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, her h-index is 3.

Thinking:

Method 1:

class Solution {
    public int hIndex(int[] citations) {
        if(citations == null || citations.length == 0) return 0;
        Arrays.sort(citations);
        int result = Integer.MIN_VALUE;
        for(int i = 0; i < citations.length; i++){
            int curH = Math.min(citations[i], citations.length - i);
            result = Math.max(curH, result);
        }
        return result;
    }
}

Second time

Also the method in the first time.

class Solution {
 public int hIndex(int[] citations) {
     if(citations == null || citations.length == 0) return 0;
     int result = 0;
     int cur = Integer.MIN_VALUE;
     Arrays.sort(citations);
     for(int i = 0; i < citations.length; i++){
         cur = Math.min(citations.length - i, citations[i]);
         result = Math.max(cur, result);
     }
     return result;
 }
}