Optimize flattening for without recursion
Last updated: May 9, 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 the nested list as input and return a flat list as output, ensuring that the solution operates in O(n) time complexity while using O(1) additional space.
Square/Block
May 9, 20264
13
3,580 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 the nested list as input and return a flat list as output, ensuring that the solution operates in O(n) time complexity while using O(1) additional space.
Coding interviews at Square/Block 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
- How would you test this solution thoroughly?
- What happens if the input contains duplicates?
- What if the input doesn't fit in memory?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires flattening a nested list of integers without using recursion. The key challenge here is to traverse the nested structure iteratively while maintaining an efficient O(n) time compl...
Approach
- Initialize an empty list called
resultto store the flattened integers. - Use a stack (or a list in Python) to keep track of elements that need to be processed. Start by pushing the entire neste...
Submit Your Answer
