“I was just asked to balance a Binary Search Tree by JFK's airport immigration”
In a away this actually makes sense. Instead of relying on automatic systems and algorithms, you rely on people, namely the agent performing the interview. A short chat about selected topics might be actually quite revealing. Point not being if you know the exact right answer for the BST question but more how you react and if there are inconsistencies in your story (most people are pretty bad at lying).All of this could be backed by the personal data has been collected before hand.The old (and often linked?) article about airport security in Israel[1] describes how the actually rely a lot on people being able to spot strange behavior.[1] http://www.huffingtonpost.com/daniel-wagner/what-israeli-air...