There were 3 interviews total. The interviewers were inexperienced and only had one solution in their mind, even though there were multiple ways to implement the solutions. The problems were not difficult. The interviewers need to be more respectful to candidates. Two of the interviewers were incredibly rude and disrespectful. Some questions they asked were personal and technically illegal. The recruiters also took a very long time to respond and did not give feedback.

A robot is located at the top-left corner of an m x n grid (marked 'Start' in the diagram below).

The robot can only move either down or right at any point in time.

The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).

How many possible unique paths are there?

Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.

Find all the elements that appear twice in this array.

Could you do it without extra space and in O(n) runtime?

Serialize and Deserialize BST