Follow up for H-Index: What if the citations array is sorted in ascending order? Could you optimize your algorithm?
Analysis:
Binary search: the first non-negative value for ciatations[i]-(len-i)
Solution:
1 public class Solution { 2 public int hIndex(int[] citations) { 3 int len = citations.length; 4 int start = 0, end = len-1; 5 while (start <= end){ 6 int mid = start + (end-start)/2; 7 if (citations[mid] >= len - mid){ 8 end = mid-1; 9 } else { 10 start = mid+1; 11 } 12 } 13 return len-start; 14 } 15 }
原文：http://www.cnblogs.com/lishiblog/p/5821477.html