Optimize flattening for without recursion
Last updated: November 24, 2025
Quick Overview
Given a nested list of integers, write a function to flatten the list into a single-level list without using recursion. The function should take the nested list as input and return a flat list containing all the integers in the same order they appear.
SentinelOne
November 24, 20251
3
2,807 solved
Given a nested list of integers, write a function to flatten the list into a single-level list without using recursion. The function should take the nested list as input and return a flat list containing all the integers in the same order they appear.
Coding interviews at SentinelOne 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
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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 parallelize this solution?
- What if the input doesn't fit in memory?
- How would you modify your solution to handle streaming input?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we are given a nested list of integers and required to flatten it into a single-level list without using recursion. The nested list can be represented as a collection of integers and ...
Approach
- Initialize an empty stack and push the entire nested list onto it.
- Create an empty list to hold the final flattened result.
- While the stack is not empty, pop an element from the stack. ...
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