LeetCode 274. H-Index

题目：
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 citatio**ns = [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.

思路：
就是要找一个作者写的文章的H-Index，h就是所有文章中有h篇的引用大于等于h，且剩下的文章引用都不超过h，并返回所有满足条件的h的最大值。

代码：

class Solution {public:    int hIndex(vector<int>& citations) {        int len=citations.size();//先求citations的长度        sort(citations.begin(),citations.end());//排序         int max=0;//max初始化为0        for(int i=len-1;i>=0;--i){//从后往前遍历            if(citations[i]>=len-i){//如果索引i对应的值大于len-i                max = len - i > max ? len - i : max;//更新max为len-i和max中的较大值            }        }        return max;    }};

输出结果： 3ms