Product Design Engineer - iPhone

Apple

Given an integer array nums where every element appears three times except for one, which appears exactly once. Find the single element and return it. You must implement a solution with a linear runtime complexity and use only constant extra space. For example, if the input is nums = [2,2,3,2], the output should be 3. Another example, if the input is nums = [0,1,0,1,0,1,99], the output should be 99. How do you solve this problem, considering edge cases like empty input, presence of zero, and negative numbers?

Apple

Let's delve into the fascinating world of computer systems. I'd like you to design a simplified operating system. Assume you're building this OS for a resource-constrained embedded system, like a smart thermostat or a simple microcontroller-based device. Your design should address the following key aspects: Memory Management: Describe your approach to memory allocation and deallocation. How would you prevent memory leaks and fragmentation in this environment? Would you use static allocation, dynamic allocation, or a combination of both? Explain your reasoning, giving specific examples of how your chosen methods would work in practice. Process/Task Scheduling: How would you schedule tasks to run on the processor? Would you opt for a preemptive or non-preemptive scheduler? What scheduling algorithm (e.g., Round Robin, Priority-based) would you use, and why? Consider the trade-offs between responsiveness, fairness, and overhead. Imagine you have three tasks: Task A (high priority, short bursts), Task B (medium priority, longer computation), and Task C (low priority, background task). How would your scheduler handle these tasks? Interrupt Handling: Explain how your OS would handle interrupts from hardware devices (e.g., a temperature sensor, a button press). How would you ensure that interrupt handlers are efficient and don't disrupt the normal operation of the system? Describe the steps involved in processing an interrupt, from the moment it occurs to the point where the interrupted task resumes execution. File System (Optional): If your embedded system requires persistent storage, outline a simple file system design. How would you organize files and directories? What data structures would you use to track file metadata (e.g., name, size, location)? How would you handle file creation, deletion, and reading/writing operations? Assume the storage medium is a small flash memory chip with limited write cycles. Inter-Process Communication (IPC): How would different tasks or processes communicate with each other within your OS? Would you use message queues, shared memory, or another mechanism? Explain the advantages and disadvantages of your chosen approach. For example, consider a scenario where one task needs to send sensor data to another task for processing. How would you implement this communication? Remember to justify your design choices based on the constraints of the embedded system, such as limited memory, processing power, and energy consumption. Aim for simplicity, efficiency, and reliability in your design. Your explanation should demonstrate a solid understanding of operating system principles and their practical application in a real-world scenario.

Apple

Let's explore your resume and then dive into a coding question. First, regarding your resume: Could you walk me through a project that you are particularly proud of? Describe your role, the challenges you faced, and the solutions you implemented. Be specific about the technologies you used and the impact your contributions had on the project's outcome. Tell me about a time you had to work with a technology or framework that you were unfamiliar with. How did you approach learning it, and how did you apply it to the project at hand? What resources did you find most helpful, and what challenges did you encounter during the learning process? Describe a situation where you had to make a trade-off between different approaches or technologies. What factors did you consider when making your decision, and how did you evaluate the potential consequences of each option? Can you provide a specific example of such a trade-off? Now, for the coding question: Given a list of integers, write a function to find the contiguous sub-array with the largest sum. For example, if the input is [-2, 1, -3, 4, -1, 2, 1, -5, 4], the output should be [4, -1, 2, 1], with a sum of 6. Explain your approach, and provide a working implementation of the function in your preferred programming language. Consider edge cases such as an empty input list or a list with only negative numbers. What is the time complexity of your solution? Can you optimize it further?