Water Infrastructure Engineer, AWS Water Team

Amazon

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree. According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself). For example: If the tree is [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1, then the expected output is 3, because the LCA of nodes 5 and 1 is 3. If the tree is [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4, then the expected output is 5, because the LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition. If the tree is [1,2], p = 1, q = 2, then the expected output is 1. Consider these constraints: The number of nodes in the tree is in the range [2, 10^5]. -10^9 <= Node.val <= 10^9 All Node.val are unique. p != q p and q will exist in the tree.

Amazon

Let's design a turnstile. A turnstile is a type of gate which allows one person to pass at a time. Consider a turnstile at a subway station. There are two panels that rotate to allow a single person passage. The turnstile has two states, Locked and Unlocked, and the customer can either Push the turnstile or Insert a token/card. Here is the state transition table: | Event | Current State | Action | Next State | | :----- | :------------ | :------------- | :--------- | | Push | Locked | | Locked | | Token | Locked | Unlock | Unlocked | | Push | Unlocked | Pass through | Locked | | Token | Unlocked | (discarded) | Unlocked | Requirements: Model the state and behavior of a simple turnstile. Implement two methods: insert_token() push() Consider edge cases and error handling. What happens if someone tries to push without inserting a token? What happens if the system malfunctions? Example: turnstile = Turnstile() print(turnstile.state) # Output: Locked turnstile.push() print(turnstile.state) # Output: Locked turnstile.insert_token() print(turnstile.state) # Output: Unlocked turnstile.push() print(turnstile.state) # Output: Locked How would you approach this design and implementation, keeping in mind scalability, maintainability, and potential future extensions such as different types of tokens or remote unlocking?

Amazon

Tell me about yourself. To help me understand your background, please structure your response by including the following: A brief overview of your educational background: Where did you go to school, what did you study, and what were your key areas of focus or specializations? A summary of your professional experience: Walk me through your previous roles, highlighting the companies you worked for, your responsibilities, and the significant projects you contributed to. Be sure to mention any accomplishments or quantifiable results you achieved. Skills and areas of expertise: What are your strongest technical skills and areas of expertise? Provide specific examples of how you've applied these skills in previous projects or roles. For instance, if you're proficient in Python, describe a project where you used Python to solve a complex problem. Your motivations and interests: What are you passionate about in the field of technology, and what motivates you to pursue a career in this area? What specific aspects of software engineering or your chosen field do you find most exciting or rewarding? Your career goals: Where do you see yourself in the next 3-5 years? What are your short-term and long-term career aspirations, and how does this role align with your overall goals? Are you looking to specialize in a particular area, take on leadership responsibilities, or make a significant impact in a specific industry? By providing this structured overview, I hope to gain a better understanding of your background, skills, and aspirations, and how they align with the goals and requirements of this position.