Google iOS Engineer Interview Guide

The technical phone interview for Google iOS Engineers typically consists of around 3 coding questions to be solved within a 45-minute time frame. During this interview, you'll be paired with a senior iOS engineer from Google.

The coding questions in this interview tend to focus heavily on computer science fundamentals, which means you'll be dealing with algorithms and data structures. While you might encounter a few iOS-specific questions, they aren't as common in this interview. The good news is that you're generally allowed to use either Objective-C or Swift for your solutions.

So, to prepare, make sure your CS fundamentals are strong and you are comfortable in both Objective-C and Swift.

A great way to prepare for the technical phone interview with Google as an iOS Engineer is to practice with mock interviews, especially with experienced Google iOS Engineers. You can find such experts on platforms like Prepfully, where you can book 1:1 sessions directly with them.

If you make it past the initial round, you'll have 5-6 interviews back-to-back.

Roughly half of these interviews will focus on algorithms and data structures, but the questions will be more challenging compared to the phone interviews. So, be prepared to tackle complex problems and demonstrate your problem-solving skills.

The other half will be iOS-specific and require a good understanding of the domain. You should have a good grasp of how computer science fundamentals apply to iOS. Topics that might come up include:

• Concurrency in iOS.
• iOS's memory management model and its distinctions from other platforms.
• Data storage methods used in iOS apps.
• iOS networking and how it differs from desktop or data centre environments.

If you're interviewing for a senior-level position, one of your interviews will focus on systems design. You won't be expected to write code for this, but you'll need to design a reasonably complex system—like a distributed database for iOS apps. Deep knowledge of iOS, including its strengths and weaknesses, is crucial in this context. Interviewers will be looking for your ability to make engineering tradeoffs.

Here's a simplified breakdown of the interview rounds and questions you'll face:

• Round 1: A coding question, typically related to String and Characters. For example, you might be asked to implement a function to reverse a linked list.
• Round 2: Behavioural questions along with a coding question. For instance, you might be asked about a challenging situation you faced in a previous job and how you handled it. The coding question could involve sorting a list of integers.
• Round 3: Another coding question, related to data structures and algorithms
• Round 4: Some iOS knowledge questions along with a few coding questions. You might be asked to explain how memory management works in iOS and then tackle a few coding questions. For example, you could be asked to implement a feature in Swift, like parsing JSON data.
• Round 5: An iOS design question where you'll need to implement the idea in Swift. For instance, you could be asked to design a system for a real-time chat application on iOS. You'd need to outline the components and architecture and possibly write Swift code to demonstrate your solution.
  
  This interview is quite similar to the one which occurs for the Doordash iOS Engineer.

Interview Questions

• You're tasked with designing a weather app for iOS. Describe the components, data sources, and user interface elements you would include, and explain the architectural pattern (e.g., MVC, MVVM) you'd use to build it.
• How does URLSession differ from NSURLConnection in iOS? Describe the key features and advantages of URLSession, and when you would choose one over the other.
• Explain the concept of Grand Central Dispatch (GCD) and when you would use it in an iOS application.
• Given an array of integers, find the longest increasing subsequence. Explain the time and space complexity of your solution.
• Add a debugging function to a view to print a tree of the view and its subviews. Follow-up: What information will be useful to print?
• Find a view with a tag and return true if the view exists, false otherwise.
• Implement a UI similar to the iOS calendar.
• Suppose users might push a large number of UIViewControllers into a UINavigationController. How would you optimise it? Code it in Swift.
• Discuss the difference between retain cycles and memory leaks in iOS. Provide an example of how you would avoid each of them.
• Describe the purpose of Auto Layout and constraints in iOS user interface design. Create a simple scenario where you'd use Auto Layout to ensure proper layout on various iOS devices
• Explain how Core Data works in iOS and discuss the advantages of using it for data storage in an app.
• Design an image-browsing app.
• How to convert a JSON file to a Dictionary type?
• How to navigate between view controllers.
• Transfer words to a digit panel.
• Given a string, find the longest substring that contains 2 unique characters. Example: ""abcbbbbcccbdddadacb" => "bcbbbbcccb".
• Implement parking garage parking and remove car functions.