H Index II is an example of Array problems. In this post we will see how we can solve it in Javascript.

Problem Description

H-Index II

Given an array of citations sorted in ascending order (each citation is a non-negative integer) of a researcher, write a function to compute the researcher's h-index.

According to the definition of h-index on Wikipedia: "A scientist has index h if h of his/her N papers have at least h citations each, and the other N − h papers have no more than h citations each."


Input: citations = [0,1,3,5,6]
Output: 3


  • [0,1,3,5,6] means the researcher has 5 papers in total
  • 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, her h-index is 3.

Note: If there are several possible values for h, the maximum one is taken as the h-index.

Follow up: This is a follow up problem to H-Index, where citations is now guaranteed to be sorted in ascending order.

Could you solve it in logarithmic time complexity?


  • case 1: citations[mid] == len-mid, then it means there are citations[mid] papers that have at least citations[mid] citations.
  • case 2: citations[mid] > len-mid, then it means there are citations[mid] papers that have moret than citations[mid] citations, so we should continue searching in the left half
  • case 3: citations[mid] < len-mid, we should continue searching in the right side. After iteration, it is guaranteed that right+1 is the one we need to find (i.e. len-(right+1) papars have at least len-(righ+1) citations)

Implementation: Please check the main.js snippet for the solution. If you have different approach in mind or have any suggestion for this implementation feel free to share in the comment below. Thanks!

Originally posted at: Github by @jeantimex