The interviewers were pleasant and helpful. The questions were programming problems based around fairly difficult puzzles and algorithms.

There were two interviews, each roughly 45 minutes long. At the end of each interview, I was asked to ask my queries.

I was required to:

• Discuss my algorithm/solution to the problem.
• Think of more efficient alternatives.
• Devise an implementation.
• Code a clean and bug-free solution on Google Docs in a language out of C++, Java, or Python.

How do you evaluate Reverse Polish Notation?

Additionally, implement a variant that also allows assigning values to variables, recalling them, and reassigning them, as an addition to RPN.