FB Phone screen chances

Had my phone screen with FB today. After a 3-4min brief introduction he asked an LC medium Binary tree root to leaf path sum question. Slightly trickier variant than LC. https://leetcode.com/problems/sum-root-to-leaf-numbers/ There was some back and forth about definition of the question. I told I will use long as output and return error for overflow to which he eventually agreed (lost few min). Coded it, interview nudged me towards simplification (spent 5 min). I answered I would use strings if tree depth was huge. I was hesitant to start wit strings because the arithmetic would take too long to code up. Time complexity I gave was O(N*d) N nodes, d is the number of digits in the number. He diverged into C++ based followup questions, lost couple of mins. 34 -36 min into the interview, he asked me second LC med question and i immediately gave optimal solution in <1min. Then he followed up with the hard variant of that question and I immediately gave the optimal approach in <1min. I wrote the main data structures for my approach i.e. map and vector, wrote code for getrandom. But he cut me of at 42 min and asked me for any questions I had. Also lost a few min coz he had a strong chinese accent and was hard to understand. https://leetcode.com/problems/insert-delete-getrandom-o1/ https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/ Main doubts I have:- Whether he perceived the optimal complexity to be different i.e O(Nh) where h is height of tree and that I didn't have time to finish code for the second question

Sum Root to Leaf Numbers - LeetCode

Leetcode

Insert Delete GetRandom O(1) - LeetCode

Leetcode

Insert Delete GetRandom O(1) - Duplicates allowed - LeetCode

Leetcode