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.

先排序，排序以后从高到低看，例如最高是8，8>=1，满足条件，次高是6，6>=2，也满足条件，一直检查到n，只要n>=序号，n就满足条件，这样找到的最大的n就是所求。

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