Find connected components in binary tree
Last updated: August 3, 2025
Quick Overview
Given a binary tree, write a function to find all the connected components within the tree, where a connected component is defined as a subset of nodes such that there exists a path between any two nodes in the subset. The function should return a list of lists, where each inner list represents a connected component. The input is the root node of the binary tree, and the output should be the connected components identified in the tree.
Elastic
August 3, 20256
15
1,106 solved
Given a binary tree, write a function to find all the connected components within the tree, where a connected component is defined as a subset of nodes such that there exists a path between any two nodes in the subset. The function should return a list of lists, where each inner list represents a connected component. The input is the root node of the binary tree, and the output should be the connected components identified in the tree.
Elastic uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
What the Interviewer Expects
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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 your solution change if the input was sorted?
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you test this solution thoroughly?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we need to identify connected components in a binary tree. A connected component is defined as a subset of nodes such that there exists a path between any two nodes in the subset. Thi...
Approach
- Initialize an empty list
componentsto store the connected components. - Create a set
visitedto keep track of visited nodes. - Define a recursive DFS function that takes a node as an argumen...
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