Leetcode 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.

计算H-index，一个关于科研人员的指标。

采用计数排序的思想解决。

class Solution {
public:
    int hIndex(vector<int>& citations) {
        vector<int> cnt(citations.size() + 2, 0);
        for(int i = 0; i < citations.size(); i++)
        {
            if(citations[i] > citations.size()) cnt[citations.size()]++;
            else cnt[citations[i]]++;
        }
        for(int i = citations.size(); i >= 0; i--)
        {
            cnt[i] += cnt[i + 1];
            if(cnt[i] >= i) return i;
        }
        return 0;
    }
};