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 otherN − h papers have no
more than h citations each." (有h篇paper至少被引用h次)

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

.

public int hIndex(int[] citations) {
		//n为文章数量
        int n=citations.length;
        //sum[]为引用次数的数组
        int sums[]=new int[n+1];

        for(int i=0;i<n;i++)
        {
        	//第i篇文章的引用次数
            int temp=citations[i];
            //如果引用次数大于文章数量
            if(temp>n)
            {
            	//引用次数设为n
                temp=n; 
            }
            //sums[temp]:引用次数大于等于temp的文章有几篇
            //sums[5] == 6:引用次数大于等于5的文章有6篇
            //这里只是++
            sums[temp]++;
        }
        for(int i=n;i>0;i--)
        {
        	//i篇文章至少被引用i次
            if(sums[i]>=i)
            {
            	//返回
                return i;
            }
            //累加
            sums[i-1]+=sums[i];
        }
        return 0;
    }