Optimize flattening for without recursion
Last updated: April 29, 2026
Quick Overview
Given a nested list of integers, implement a function to flatten the list into a single list of integers without using recursion. The function should take a nested list as input and return a flat list as output, ensuring that the solution is optimized for both time and space complexity.
SpaceX
April 29, 20268
11
933 solved
Given a nested list of integers, implement a function to flatten the list into a single list of integers without using recursion. The function should take a nested list as input and return a flat list as output, ensuring that the solution is optimized for both time and space complexity.
Coding interviews at SpaceX 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
- What if the input doesn't fit in memory?
- Can you solve this iteratively instead of recursively (or vice versa)?
- Can you optimize the space complexity of your solution?
- How would your solution change if the input was sorted?
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Problem Analysis
To flatten a nested list of integers without using recursion, we can observe that this is a problem that can be effectively tackled using an iterative approach, specifically utilizing a stack data str...
Approach
- Initialize an empty list
resultto hold the flattened integers and a stack initialized with the input nested list. - While the stack is not empty, pop the top element from the stack.
- Check if...
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