H-Index ——Leetcode

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.

题目大意：给一个数组，是一个科学家各个paper的引用数，求最大的hindex，hindex就是有h篇不低于h引用的paper。

解题思路：首先排个序，然后倒序走一遍更新res就可以了。

　　public int hIndex(int[] array) {
        if (array == null || array.length == 0) {
            return 0;
        }
        Arrays.sort(array);
        int len = array.length;
        int pos = len - 1;
        int res = 0;
        while (pos >= 0) {
            int tmp = Math.min(len-pos,array[pos]);
            res = Math.max(res, tmp);
            pos--;
        }
        return res;
    }