Startups tend to ask questions aimed at building or debugging code. For example, “Write a function that takes two rectangles and figures out if they overlap.” They'll care more about progress than perfection.

Larger companies will want to test your general know-how of data structures and algorithms. For instance, “Write a function that checks if a binary tree is ‘balanced’ in O(n) time.” They'll care more about how you solve and optimize a problem.

Implement stack using two queues