The interview had two stages.

First, a telephonic interview, and then a Hangouts call.

In the telephonic interview, I was asked about normal problems and some puzzles, like:

If an egg is dropped from above that floor, it will break. If it is dropped from that floor or below, it will be completely undamaged, and you can drop the egg again.

Given two eggs, find the highest floor an egg can be dropped from without breaking, with as few drops as possible.

In the Hangouts call, I was asked about dynamic programming, data structures, probability, graphs, BFS, and DFS.

A string consists of '0', '1', and '?'.

The question mark can be either '0' or '1'.

Find all possible combinations for such a string.