Best (technical) interview questions

[Paddy]

[TheDude]

What is the best technical question you have been asked in an interview.

For me it was:

There is a robot on an infinite staircase - we have a single function step() that will cause the robot to take a single step up or down at random and return true or false accordingly.

Write a function stepUp() that will return only once the robot has taken a single step up.

Follow up questions:

1. Is your implementation guaranteed to work? What possible problems do you see with this approach?

2. Implement stepUp() without any local variables.