274. H-Index

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.

代码如下：

 public class Solution {
     public int hIndex(int[] citations) {
         if(citations.length==0)
         return 0;

         Arrays.sort(citations);
         if(citations[citations.length-1]==0)
         return 0;
         if(citations[0]>=citations.length)
         return citations.length;
         int length=0;
        for(int i=0;i<citations.length;i++)
        {
            length=citations.length-i;
            if(citations[i]>=length)
            {
                int count=0;
                if(citations[i]>=length)
                {
                    for(int j=0;j<i;j++)
                    {
                        if(citations[j]>=length)
                        count++;
                    }
                    if(count<=length)
                    return length;
                }
            }
        }
        return length;
     }
 }