Design an In-Memory Unix File System
Last updated: September 4, 2025
Quick Overview
Implement a class with mkdir, ls, addContentToFile, and readContentFromFile methods. Tests OOP design, trie/hashmap usage, and edge case handling.
Perplexity
September 4, 202512
9
4,750 solved
Implement a class with mkdir, ls, addContentToFile, and readContentFromFile methods. Tests OOP design, trie/hashmap usage, and edge case handling.
Reported directly by Perplexity candidates. Tests practical OOP design and data structure selection for hierarchical data.
What the Interviewer Expects
- Design a clean class interface with proper method signatures
- Use a trie or nested dictionary for path representation
- Handle edge cases: root directory, empty paths, non-existent paths
- Support both files and directories at the same path level
- Write clean, readable Python code
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you add support for deleting files?
- How would you implement file permissions?
- What data structure would you use for efficient ls on large directories?
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Problem Analysis
The problem requires designing an in-memory Unix file system, which involves managing directories and files using a structured approach. A trie (prefix tree) is a suitable data structure for this prob...
Approach
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Define a TrieNode class: Each node has a dictionary for children (representing directories and files), a boolean to indicate if it's a file, and a content string for file content.
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**Impleme...
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