After sorting in descending order, iterate through the list and find the first index where the citation count is less than the index + 1 (0-based). The h-index is this index.

Use binary search on the sorted list to efficiently find the h-index, comparing the middle element to its position to determine the search direction.

Optimize space by avoiding a full sort—use a counting sort approach if the maximum citation count is within a reasonable range (e.g., ≤ 1000), then compute the h-index from the frequency array.