LeetCode in Kotlin

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.length
• 1 <= n <= 5000
• 0 <= citations[i] <= 1000

Solution

class Solution {
    fun hIndex(citations: IntArray): Int {
        val counts = IntArray(citations.size + 1)
        for (citation in citations) {
            val idx = (citations.size).coerceAtMost(citation)
            counts[idx] += 1
        }
        var total = 0
        for (i in counts.indices) {
            val idx = citations.size - i
            total += counts[idx]
            if (total >= idx) {
                return idx
            }
        }
        return 0
    }
}

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