LeetCode Top Interview 150
274. H-Index
Medium
Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper, return compute the researcher’s h-index.
According to the definition of h-index on Wikipedia: A scientist has an index h if h of their n papers have at least h citations each, and the other n − h papers have no more than h citations each.
If there are several possible values for h, the maximum one is taken as the h-index.
Example 1:
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, their h-index is 3.
Example 2:
Input: citations = [1,3,1]
Output: 1
Constraints:
n == citations.length1 <= n <= 50000 <= citations[i] <= 1000
Solution
from typing import List
class Solution:
def hIndex(self, citations: List[int]) -> int:
n = len(citations)
freq = [0] * (n + 1)
for c in citations:
freq[min(c, n)] += 1
total = 0
for h in range(n, 0, -1):
total += freq[h]
if total >= h:
return h
return 0