openai | Software Engineer | Interview Experience
Interview Date: Not specified
Result: Not specified
Difficulty: Not specified
Interview Process
The interview focused on implementing a memory allocation system. The task involved creating a class that initializes with a total memory size and supports allocate and free operations, returning the address of the allocated size. The memory blocks must be contiguous, and errors should be reported for illegal operations or if allocation is not possible.
The candidate considered two approaches for the implementation: linked lists and balanced binary trees. Due to time constraints, they opted for a doubly linked list to manage free blocks, storing both the size and starting address. The allocation process involved traversing the list to find the first suitable block. If the free block size was greater than the requested size, it would adjust the size; if equal, it would delete the node. The free operation handled several cases, including adding in the middle and merging with adjacent blocks.
The candidate completed the implementation in about half an hour, considering edge cases and running through sample test cases. However, a pointer operation error was identified during the review. The candidate discussed the space-time complexity (O(n)), potential flaws in the algorithm (such as fragmentation), and proposed solutions, including dedicating space for small block requests and using a best-fit strategy instead of first-fit, which is slower. They also suggested using a balanced binary tree to improve allocation time to O(log n).
The interview atmosphere was cordial, and the interviewer wished the candidate good luck for future interviews. Despite feeling confident about their performance, the candidate received a rejection letter two days later.
Technical Questions
- Implement a memory allocation system (Data Structures)
Tips & Insights
- Be thorough in checking for edge cases in your code.
- Understand the implications of your algorithm’s complexity and potential flaws.
- Communicate clearly during the interview and engage with the interviewer about your thought process.