I received this interview after dropping my resume at an internal intern open house. I received an interview invitation within the next three days. The interview process consisted of three back-to-back 45-minute rounds.

Two technical rounds and one behavioral round.

The first interview was technical, and I was asked to solve a data structure problem. The second interview was behavioral, and I was asked about my background in coding, previous projects, and exposure to mobile development. Lastly, the third interview was a fairly easy and straightforward technical question about OOP and a simple string manipulation question. We briefly covered Big O Notation. All my interviewers were pleasant and made an effort to keep the interviews lighthearted and friendly.

Create an LRU cache that can hold five objects maximum at a time, and write the get, add, and remove functions for it. If you add an item to the cache when it already contains five items, the least recently accessed item should be removed, and your new item should be added to the top of the cache.

Given a string, return the first letter that does not have a duplicate. Discuss the time efficiency of your solution and then rewrite the solution to be space-efficient.