275. H-Index II

Question

Given an array of citations sorted in ascending order (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 = [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, her h-index is 3.

Thinking:

Method 1:

class Solution {
    public int hIndex(int[] citations) {
        if(citations == null || citations.length == 0) return 0;
        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(result, curH);
        }
        return result;
    }
}

Second time

This question is the follow up question of the previous one, and it’s easier.

class Solution {
 public int hIndex(int[] citations) {
     if(citations == null || citations.length == 0) return 0;
     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(result, curH);
     }
     return result;
 }
}