You had two questions: one was easy and familiar, the other was more difficult. You had 45 minutes to solve both questions.

The difficult one was a graph question. It sounded similar to the lowest common ancestor in a tree problem, but I wasn't familiar with this question during the interview. Also, the graph being given in an array was confusing to me, especially the direction of the edges for each tuple.

Given a Directed Acyclic Graph (DAG) and two vertices, find if the two vertices have a common ancestor.

Example: [(1,2),(3,4),(1,3),(5,4)]

• Vertices 2 and 4 have 1 as a common ancestor, so it returns true.
• Vertices 3 and 5 do not have a common ancestor, so it should be returned false.