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275. H Index II

Array Binary Search

Problem - 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 non-descending order, return the researcher's h-index.

According to the definition of h-index on Wikipedia: The h-index is defined as the maximum value of h such that the given researcher has published at least h papers that have each been cited at least h times.

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.length
  • 1 <= n <= 105
  • 0 <= citations[i] <= 1000
  • citations is sorted in ascending order.

Solutions

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class Solution:
    def hIndex(self, citations: List[int]) -> int:
        n = len(citations)
        left, right = 0, n

        while right > left:
            mid = (left + right + 1) // 2
            if (citations[n - mid] >= mid):
                left = mid
            else:
                right = mid - 1

        return left

Submission Stats:

  • Runtime: 0 ms (100.00%)
  • Memory: 23 MB (74.38%)