H-Index II

Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?
Hint:
Expected runtime complexity is in O(log n) and the input is sorted.
Solution:
1. public class Solution {
2. public int hIndex(int[] citations) {
3. int n = citations.length;
4. int lo = 0, hi = n - 1;
5. 6. while (lo <= hi) {
7. int mid = lo + (hi - lo) / 2;
8. 9. if (citations[mid] >= n - mid) {
10. hi = mid - 1;
11. } else {
12. lo = mid + 1;
13. }
14. }
15. 16. return n - 1 - hi;
17. }
18. }