LeetCode OJ：H-Index（H指数）

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.

感觉这题更加像动归，没写出来，看了别人的实现，代码如下：

 class Solution {
 public:
     int hIndex(vector<int>& citations) {
         int n = citations.size();
         vector<int>index(n + , );//注意这里是n+1
         for(int i = ; i < n; ++i){
             if(citations[i]>=n)
                 index[n]++;
             else
                 index[citations[i]]++;
         }
         if(index[n] >= n) return n;
         for(int i = citations.size()-; i >= ; --i){
             index[i]+=index[i+];
             if(index[i] >= i)
                 return i;
         }
         return ;
     }
 };