I applied through Facebook's website for university recruiting. I received an email from their recruiter within two days and scheduled a telephone interview for two weeks later. The interview was supposed to be a technical interview using CollabEdit.

The interview started with basic behavioral questions, such as, "What is the most exciting thing you have done till now?" My speaking skills are very subpar, so I fumbled a lot while answering behavioral questions.

Then I was asked to suggest an algorithm to print the nodes of a binary tree in their vertical order. For example:

  a
 / \
b   c
   / \
  d   e
 / \
f   g

The expected output is: b f a d c g e.

I solved the question without much of the interviewer's help in under five minutes. Then I was asked to code this in CollabEdit, which I almost completed, except for some small issues with the hash map.

The interview ended. I was pretty confident of being selected for this round. However, I was told via email by my recruiter that they could not move forward with my application (heartbreak).

Till today, I refresh my inbox, hopelessly waiting for an email stating there was some error.

Print the nodes of a binary tree columnwise.

For example:

Input: a /
b c /
d e /
f g

Then output is:

b f a d c g e