Optimize flattening for streaming input
Last updated: February 7, 2026
Quick Overview
Given a stream of nested lists, implement a function that efficiently flattens the lists into a single list while maintaining the order of elements. The function should handle varying levels of nesting and return the flattened list as output. Ensure that the solution can process the streaming input without requiring the entire dataset to be stored in memory at once.
Snowflake
February 7, 202633
6
1,964 solved
Given a stream of nested lists, implement a function that efficiently flattens the lists into a single list while maintaining the order of elements. The function should handle varying levels of nesting and return the flattened list as output. Ensure that the solution can process the streaming input without requiring the entire dataset to be stored in memory at once.
Coding interviews at Snowflake 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
- Can you solve this in a single pass?
- How would your solution change if the input was sorted?
- What happens if the input contains duplicates?
- How would you test this solution thoroughly?
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Problem Analysis
To efficiently flatten a stream of nested lists, we will use a recursive approach that utilizes a stack to manage the elements as we encounter nested structures. This method is suitable because it all...
Approach
- Initialize an empty list
resultto store the flattened elements. - Define a helper function
flattenthat takes an input (which can be either a list or an element). - In
flatten, check i...
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