274 H-Index

🔀 Pick One

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.length
  • 1 <= n <= 5000
  • 0 <= citations[i] <= 1000
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class Solution:
    def hIndex(self, citations: List[int]) -> int:
        n = len(citations)
        counts = [0] * (n + 1)
        for c in citations:
            counts[min(n, c)] += 1
        acc = 0
        for i in range(n, -1, -1):
            acc += counts[i]
            if acc >= i:
                return i
        return 0

'''
One-line
'''
class Solution:
    def hIndex(self, citations: List[int]) -> int:
        return sum(i < j for i, j in enumerate(sorted(citations, reverse=True)))
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func hIndex(citations []int) int {
	buckets := make([]int, len(citations)+1)
	length := len(citations)
	for _, c := range citations {
		if c >= length {
			buckets[length]++
		} else {
			buckets[c]++
		}
	}

	count := 0
	for i := length; i > 0; i-- {
		count += buckets[i]
		if count >= i {
			return i
		}
	}
	return 0
}