LeetCode in Kotlin
275. H-Index II
Medium
Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper and citations is sorted in an ascending order, 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.
You must write an algorithm that runs in logarithmic time.
Example 1:
Input: citations = [0,1,3,5,6]
Output: 3
Explanation: [0,1,3,5,6] means the researcher has 5 papers in total and each of them had received 0, 1, 3, 5, 6 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 = [1,2,100]
Output: 2
Constraints:
n == citations.length1 <= n <= 1050 <= citations[i] <= 1000citationsis sorted in ascending order.
Solution
class Solution {
fun hIndex(citations: IntArray): Int {
var lo = 1
var hi = 1000
var ans = 0
while (lo <= hi) {
val mid = (lo + hi) / 2
val p = check(mid, citations)
if (citations.size - p >= mid) {
ans = mid
lo = mid + 1
} else {
hi = mid - 1
}
}
return ans
}
private fun check(v: Int, arr: IntArray): Int {
var lo = 0
var hi = arr.size - 1
while (lo <= hi) {
val mid = (lo + hi) / 2
if (arr[mid] < v) {
lo = mid + 1
} else {
hi = mid - 1
}
}
return lo
}
}