Research Scientist, Machine Learning (PhD)

Meta

Implement a SnapshotArray that supports the following interface: SnapshotArray(int length) initializes an array-like data structure with the given length. Initially, each element equals 0. void set(index, val) sets the element at the given index to be equal to val. int snap() takes a snapshot of the array and returns the snap_id: the total number of times we called snap() minus 1. int get(index, snap_id) returns the value at the given index, at the time we took the snapshot with the given snap_id For example: Input: [SnapshotArray,set,snap,set,get] [[3],[0,5],[],[0,6],[0,0]] Output: [null,null,0,null,5] Explanation: SnapshotArray snapshotArr = new SnapshotArray(3); // set the length to be 3 snapshotArr.set(0,5); // Set array[0] = 5 snapshotArr.snap(); // Take a snapshot, return snap_id = 0 snapshotArr.set(0,6); snapshotArr.get(0,0); // Get the value of array[0] with snap_id = 0, return 5 What data structures and algorithms are best suited for this problem? What are the time and space complexities of each operation?

Meta

Let's design a database for a library. Consider the following requirements: Books: The library has a collection of books. Each book has a title, an author (or authors), a publication year, an ISBN, and a genre. A book can have multiple authors. Members: The library has members who can borrow books. Each member has a unique member ID, a name, an address, and a phone number. Borrowing: The library needs to keep track of which books are borrowed by which members and when they are borrowed and returned. A member can borrow multiple books, and a book can be borrowed by multiple members over time. Reservations: Members can reserve books that are currently checked out. The system needs to keep track of reservations and their order. Late Fees: The library charges late fees for overdue books. The system needs to calculate and track these fees. Based on these requirements, design a relational database schema. Include the tables, columns, data types, primary keys, and foreign keys. Provide a brief explanation for each table and the relationships between them. How would you handle the many-to-many relationship between books and authors? How would you handle the many-to-many relationship between members and borrowed books? How would you ensure data integrity, such as preventing a member from borrowing the same book twice at the same time?

Meta

Could you describe a situation where you faced a significant memory leak issue in a C++ application and how you diagnosed and resolved it? Please walk me through the tools and techniques you used, the challenges you encountered, and the ultimate solution you implemented. For example, imagine you're working on a large-scale C++ application for processing high-volume financial transactions. The application is experiencing performance degradation over time, eventually leading to crashes. After initial investigation, you suspect a memory leak. Describe your approach to identifying the source of the leak. Consider discussing the specific tools you might employ, such as memory profilers (e.g., Valgrind, AddressSanitizer), debugging techniques (e.g., heap analysis), and code review strategies. What were some of the initial hypotheses you formed, and how did you validate or refute them? What were the key code areas you focused on based on your initial findings? Furthermore, explain any specific coding practices or patterns that contributed to the leak (e.g., improper use of smart pointers, forgetting to release dynamically allocated memory). How did you correct these issues, and what steps did you take to prevent similar leaks from occurring in the future? Did you implement any automated testing or monitoring to detect memory leaks early on? Finally, reflect on any lessons learned from this experience and how it has shaped your approach to memory management in C++.