My interview process had 5 steps:

• Initial screening
• Technical interview
• Live coding interview
• Algorithmic interview
• Team fit interview

In total, it took around one month. In the end, I was rejected with some strange explanations.

It seems like Team Fit was the most important one, so it's a good question why they don't start with it instead of a long technical interviews chain.

During the technical interview, I was asked about Swift and iOS topics:

• Generics
• Generic protocols
• How Swift Optionals work
• The difference between closures and functions
• How memory is allocated for closures
• Capturing values in closures
• The difference between structs and classes
• How memory is allocated for structs and classes, including edge cases (struct in heap, class in stack)

After that, I was shown different code samples and tasks:

• A DispatchQueue "spaghetti" task (to determine execution order)
• An execution order task
• A Unit-Testing sample task (to improve code and create a proper test)
• A retain cycle task (to find the cycle or prove there were no problems)

During Live Coding, I had a small app to write. The purpose of this app was to parse a local JSON file with geo points and place these points on a MapKit map. The solution needed to be clear, testable, scalable, and support later migration from a local file to a remote data source. Things to consider included architecture and error handling.

During the Algorithmic interview, I was first asked about common Computer Science concepts:

• What happens when a user inputs a query in a browser and presses Enter. This led to discussions about DNS, the 7 OSI layers, HTTPS/HTTP, TLS, TCP/UDP connections, and JSON/XML.
• How a HashMap works and its time complexity for adding/getting an element. This led to discussions about hash functions and collisions.
• OOP, inheritance, and composition (advantages and disadvantages).

The second part was the algorithmic task itself: "You are given an array A of non-negative numbers and a target sum S. Write an efficient function that finds one continuous sub-sequence of elements which sum up to precisely S. The return value should be a pair of array indices or an empty array."