SRE Engineer

Apple

Given two integer arrays inorder and postorder where inorder is the inorder traversal of a binary tree and postorder is the postorder traversal of the same tree, construct and return the binary tree. For example: Example 1: inorder = [9,3,15,20,7], postorder = [9,15,7,20,3] Expected Output: [3,9,20,null,null,15,7] Example 2: inorder = [-1], postorder = [-1] Expected Output: [-1] 1 <= inorder.length <= 3000 postorder.length == inorder.length -3000 <= inorder[i], postorder[i] <= 3000 inorder and postorder consist of unique values. Each value of postorder also appears in inorder. inorder is guaranteed to be the inorder traversal of the tree. postorder is guaranteed to be the postorder traversal of the tree.

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

Tell me about the most difficult project you've ever worked on and how you managed to deliver. To provide context, please consider these aspects: What were the specific challenges? For example, was it a tight deadline, limited resources, a novel technology, ambiguous requirements, or conflicting stakeholder expectations? Elaborate on the nature and magnitude of these challenges. What role did you play? Were you leading the project, a core contributor, or in a support role? Describe your responsibilities and level of autonomy. What specific actions did you take to overcome these challenges? Did you implement any specific strategies, tools, or methodologies? Did you have to make any difficult decisions or trade-offs? Provide concrete examples of your problem-solving approach, technical skills, and leadership abilities. How did you collaborate with your team and stakeholders? Describe how you communicated progress, resolved conflicts, and ensured alignment among team members and stakeholders. Did you have to manage any difficult personalities or navigate any political sensitivities? What were the results of your efforts? Did you successfully deliver the project? Did you meet or exceed expectations? What were the key lessons learned from this experience? Quantify your accomplishments whenever possible (e.g., reduced costs by X%, improved efficiency by Y%). For instance, perhaps you spearheaded the development of a new machine learning model with a very aggressive timeline while dealing with constantly shifting requirements from the business team and a lack of readily available training data. Or maybe you were tasked with migrating a legacy system to a modern cloud-based architecture with limited budget and a team with varying levels of expertise. Or consider a situation where you were responsible for launching a new product feature under immense pressure from senior management, requiring you to make tough calls on scope and prioritize ruthlessly. Share your story, highlighting the obstacles you faced and how you successfully navigated them.