LeetCode [274] H-Index

 274. H-Index

Medium

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."

Example:

Input: citations = [3,0,6,1,5]
Output: 3 
Explanation: [3,0,6,1,5] 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, her h-index is 3.

Note: If there are several possible values for h, the maximum one is taken as the h-index.

1 2 3 4 5 6 7 8 9 10 11 12 13

//C++: 4ms class Solution { public: int hIndex(vector<int>& citations) { sort(citations.begin(), citations.end(), greater<int>()); int n = citations.size(); int i = 0; for(; i<n; ++i){ if(citations[i]<i+1) break; } return i; } };

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

class Solution { public int hIndex(int[] citations) { int n = citations.length; int[] buckets = new int[n+1]; for(int c : citations) { if(c >= n) { buckets[n]++; } else { buckets[c]++; } } int count = 0; for(int i = n; i >= 0; i--) { count += buckets[i]; if(count >= i) { return i; } } return 0; } }