I applied online and received a phone interview request within 3 weeks.

On the phone, I was asked two technical questions:

• The first was to find the loop in a linked list.
• The second was a bit different. My interviewer asked me to consider a function shaped as an S-curve in the x-y plane, which is always increasing. Then he asked me to find the corresponding x-value for a given y-value (the function was a black-box function; I didn't know what it does).

He was very helpful and guided me to the correct answers for both questions.

After the phone interview, I received the invitation for an in-house interview within 3 days. I went to Bloomberg Tower, which was quite fascinating (the view from the 29th floor, etc.).

In the interview process, I only survived two rounds.

In the first round, there were three people: two interviewers and one person monitoring the process. The questions were:

1. How to maximize the profit from tomorrow's stock information, given that I could perform two transactions: one buy and one sell. I needed to find the best buy and sell points to maximize my profit.

2. In a string containing parentheses, curly brackets, and square brackets, how to validate if the string is correct (i.e., every opened parenthesis, curly bracket, and square bracket must be closed before the string ends).

   • The correct answer was to push special characters onto a stack and then check them.

The questions were not that hard, but I failed to provide the answers within 45 minutes, and my interviewers helped me go through the solutions.

In the second round, there was only one interviewer (most probably the project manager) who asked me some basic questions at first, starting with my resume, then the difference between a list and a vector, and the complexity of the push_back function in a vector. Then he moved on to the main question:

1. Add a sibling pointer to a complete binary search tree. In every level of the tree, the right node would be the sibling of the current node. The rightmost node's sibling pointer at each level should be set to NULL. Here is an example:

     5
   

   3 7 2 4 6 8

In this BST, 7 is the sibling of 3. 4 is the sibling of 2. 6 is the sibling of 4, etc. 5, 7, and 8 have sibling pointers set to NULL.

He helped me find the correct answer, but I failed to write the code for it within 45 minutes.

After this interview, he escorted me to the building's entrance and told me I would receive the answer within a few days.

Maximizing the profit