I had two phone interviews and failed the second one. Both interviews used a collaborative text editor for code-related questions.

The first interview covered a range of topics.

• I was asked to name five two-letter Unix commands.
• I was asked how to find the number of files in a directory and all its subdirectories.

The next topic was functional programming.

• I had to explain what a fold is.
• I had to write down the type of a fold function (in a language of my choice, not necessarily OCaml).

I was asked about tail recursion and tail calls in general.

Then, I had to write a function returning all permutations of a list (again, in a language of my choice).

I was asked if I knew what memoization is and had to write a function that returned a memoized version of a passed-in function. We then discussed the problems with my implementation: the cache I used would grow larger whenever the function was called with new elements.

There is a company, modelled as a tree of employees and the people reporting to them. Every employee has a fun value. At a party, every employee only has fun if his direct boss is not at the party. Otherwise, he adds fun corresponding to his fun value to the party. Write code to find the maximum total fun that can be had at the party.