274. H-Index

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