The interview process began at a fast pace, with five interviews occurring over the first week (two interviews per day).

Following this intense period, there was a silent period, then an even longer silent period, before the on-site round invitation arrived in my inbox.

I completed the on-site round via Skype due to some visa issues.

The quality of the interaction seemed to decline as time went on.

I recall the interviewer from the initial round enthusiastically showing me some impressive features of the Bing Images service then in deployment – I was genuinely excited to see it all.

However, I also distinctly remember this same individual during the final on-site interview stating, with evident annoyance because I couldn't provide a satisfactory answer: "You have good coding skills, but you're not good at solving problems, and we need someone who can solve problems."

This remark felt quite rude, especially considering I had successfully solved problems in the seven previous interviews. Nevertheless.

During an introductory interview, I was asked the following:

• How to check if a given tree is a subtree of another tree.
• Given a function that returns a random integer value between 1 and 2 (with the same probability), build a function that returns a random integer between 1 and 3 (also with the same probability).
• Write the code to serialize and deserialize a tree.
• How would you implement an "infinity scroll" feature in a web app? Discuss design and implementation issues.
• How would you implement an image service? Again, discuss design and implementation issues.
• Implement a divide and conquer pow function without recursion.
• Write a program to sort a file that is several terabytes in size on a machine that only has 2GB of RAM.
• Given a file with N words, return the minimum number of words such that, together, these words contain all the alphabet letters.
• Write an algorithm to efficiently solve a crossword puzzle. (This is where I failed.)

Of course, you have to always give the complexity of the solutions you propose and try to find the optimal one.