I was contacted directly by them after uploading my resume on their website.

The first phone call was a quick screening.

This was followed by a second phone call with an engineer, during which I used a screen-sharing website/IDE to answer a technical question. They then modified the question, asked me to make improvements, and to provide its time and space complexities.

The response was pretty quick (2-3 days) before they invited me for an on-site interview.

The on-site consisted of three whiteboard questions, a programming section, and a non-technical interview, spanning the entire workday.

Given two points on a directed acyclic graph (DAG), determine their least common ancestor.

Provide its time complexity and describe any improvements you could make, if possible.