I received a call from a recruiter for a technical phone screen. She mentioned I would be expected to solve two DSA questions.

I was asked one DSA question: "Find leaves of a binary tree" (a LeetCode question). I was able to provide an optimal approach within 15 minutes. The interviewer didn't understand it and moved on to ask about 1NF, the difference between a unique key and a primary key, and indexing.

He also asked another coding question in the last 10 minutes. I was able to provide an answer to the first part.

Find leaves of binary tree (https://leetcode.com/problems/find-leaves-of-binary-tree/)

Given $n$ balls of unequal weight and a weighing scale with two pans, what are the minimum comparisons needed to find the heaviest ball? (Answer: $n-1$)

What are the minimum comparisons needed for the $m$ heaviest balls?

Maintaining a max heap will give the minimum comparison.