I was contacted by a recruiter. They were very friendly and punctual.

My initial phone screening was a rapid round of simple questions about complexity and sorting algorithms.

After that, there was a coding round, which I could not clear.

Given two strings, A and B, of the same length n, find whether it is possible to cut both strings at a common point such that the first part of A and the second part of B form a palindrome.

You have 52 playing cards (26 red, 26 black). You draw cards one by one. A red card pays you a dollar. A black one fines you a dollar. You can stop any time you want. Cards are not returned to the deck after being drawn. What is the expected payoff following this optimal rule?

For this, you need to find what is the optimal stopping rule in terms of maximizing expected payoff.