I received a call from a third-party recruiter, and they scheduled my interview for the weekend.

When I arrived, I saw there were around 10-15 candidates. I had to wait a long time because the interview panel consisted of only two people (possibly three).

The first round was for data structures and algorithms. The interviewer didn't understand the difference between time complexity and space complexity (I'm not kidding).

For one problem, I proposed two solutions, explaining that the choice depended on whether the requirement involved using extra space. He seemed confused and kept asking for the "best" solution.

Another question was to implement a queue using a stack. First, he asked me to implement the pop and push methods. I then asked if he meant enqueue and dequeue. The solution for this problem involves using two stacks, but the interviewer insisted I use only one. Later, I realized he didn't consider that recursive function calls also utilize the function call stack.

He asked me 4-5 problems, and I am 100% sure I answered each correctly.

After that, there was an iOS round, which was also quite easy. Most of the questions were from common resources for iOS interview questions. I believe I answered everything correctly.

I later found out I was rejected. I know what you might be thinking: perhaps I misbehaved during the interview. I was very polite and patient.

Implement queue using stacks.

Design the back-end part of a search query (like ES).

Implement Trie DS.

What is the difference between a frame and a bound?

How does GCD work?

Have you ever used NSOperationQueue?

How does Auto Layout work?