Optimize flattening for O(1) space
Last updated: October 29, 2025
Quick Overview
Given a nested list of integers, implement a function to flatten the list into a single-level list while using O(1) space. The function should modify the input list in place and return the flattened list as output. Ensure that the solution efficiently handles varying levels of nesting without using additional data structures.
Morgan Stanley
October 29, 202544
14
3,553 solved
Given a nested list of integers, implement a function to flatten the list into a single-level list while using O(1) space. The function should modify the input list in place and return the flattened list as output. Ensure that the solution efficiently handles varying levels of nesting without using additional data structures.
Coding interviews at Morgan Stanley focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
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
- Can you optimize the space complexity of your solution?
- What if the input doesn't fit in memory?
- How would you parallelize this solution?
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Problem Analysis
The problem requires us to flatten a nested list of integers into a single-level list in place, using O(1) space. This suggests that we cannot use any additional data structures such as stacks or queu...
Approach
- Initialization: Start with an index pointer set to 0, which will track our current position in the list.
- Loop Through the List: Use a while loop that continues until the current index ...
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